diff --git a/frontends/api/main.py b/frontends/api/main.py
index 72d9f81..fc6ec56 100644
--- a/frontends/api/main.py
+++ b/frontends/api/main.py
@@ -3,7 +3,7 @@
 Stegasoo REST API
 
 FastAPI-based REST API for steganography operations.
-Designed for integration with other services and automation.
+Supports both text messages and file embedding.
 """
 
 import io
@@ -28,6 +28,8 @@ from stegasoo import (
     DAY_NAMES, __version__,
     StegasooError, DecryptionError, CapacityError,
     has_argon2,
+    FilePayload,
+    MAX_FILE_PAYLOAD_SIZE,
 )
 from stegasoo.constants import (
     MIN_PIN_LENGTH, MAX_PIN_LENGTH,
@@ -42,7 +44,7 @@ from stegasoo.constants import (
 
 app = FastAPI(
     title="Stegasoo API",
-    description="Secure steganography with hybrid authentication",
+    description="Secure steganography with hybrid authentication. Supports text messages and file embedding.",
     version=__version__,
     docs_url="/docs",
     redoc_url="/redoc",
@@ -79,6 +81,20 @@ class EncodeRequest(BaseModel):
     date_str: Optional[str] = None
 
 
+class EncodeFileRequest(BaseModel):
+    """Request for embedding a file (base64-encoded)."""
+    file_data_base64: str
+    filename: str
+    mime_type: Optional[str] = None
+    reference_photo_base64: str
+    carrier_image_base64: str
+    day_phrase: str
+    pin: str = ""
+    rsa_key_base64: Optional[str] = None
+    rsa_password: Optional[str] = None
+    date_str: Optional[str] = None
+
+
 class EncodeResponse(BaseModel):
     stego_image_base64: str
     filename: str
@@ -97,7 +113,12 @@ class DecodeRequest(BaseModel):
 
 
 class DecodeResponse(BaseModel):
-    message: str
+    """Response for decode - can be text or file."""
+    payload_type: str  # 'text' or 'file'
+    message: Optional[str] = None  # For text
+    file_data_base64: Optional[str] = None  # For file (base64-encoded)
+    filename: Optional[str] = None  # For file
+    mime_type: Optional[str] = None  # For file
 
 
 class ImageInfoResponse(BaseModel):
@@ -112,6 +133,7 @@ class StatusResponse(BaseModel):
     version: str
     has_argon2: bool
     day_names: list[str]
+    max_payload_kb: int
 
 
 class ErrorResponse(BaseModel):
@@ -129,7 +151,8 @@ async def root():
     return StatusResponse(
         version=__version__,
         has_argon2=has_argon2(),
-        day_names=list(DAY_NAMES)
+        day_names=list(DAY_NAMES),
+        max_payload_kb=MAX_FILE_PAYLOAD_SIZE // 1024
     )
 
 
@@ -173,7 +196,7 @@ async def api_generate(request: GenerateRequest):
 @app.post("/encode", response_model=EncodeResponse)
 async def api_encode(request: EncodeRequest):
     """
-    Encode a secret message into an image.
+    Encode a text message into an image.
     
     Images must be base64-encoded. Returns base64-encoded stego image.
     """
@@ -194,8 +217,55 @@ async def api_encode(request: EncodeRequest):
         )
         
         stego_b64 = base64.b64encode(result.stego_image).decode('utf-8')
+        day_of_week = get_day_from_date(result.date_used)
         
-        # Get day of week from the date used
+        return EncodeResponse(
+            stego_image_base64=stego_b64,
+            filename=result.filename,
+            capacity_used_percent=result.capacity_percent,
+            date_used=result.date_used,
+            day_of_week=day_of_week
+        )
+        
+    except CapacityError as e:
+        raise HTTPException(400, str(e))
+    except StegasooError as e:
+        raise HTTPException(400, str(e))
+    except Exception as e:
+        raise HTTPException(500, str(e))
+
+
+@app.post("/encode/file", response_model=EncodeResponse)
+async def api_encode_file(request: EncodeFileRequest):
+    """
+    Encode a file into an image (JSON with base64).
+    
+    File data must be base64-encoded.
+    """
+    try:
+        file_data = base64.b64decode(request.file_data_base64)
+        ref_photo = base64.b64decode(request.reference_photo_base64)
+        carrier = base64.b64decode(request.carrier_image_base64)
+        rsa_key = base64.b64decode(request.rsa_key_base64) if request.rsa_key_base64 else None
+        
+        payload = FilePayload(
+            data=file_data,
+            filename=request.filename,
+            mime_type=request.mime_type
+        )
+        
+        result = encode(
+            message=payload,
+            reference_photo=ref_photo,
+            carrier_image=carrier,
+            day_phrase=request.day_phrase,
+            pin=request.pin,
+            rsa_key_data=rsa_key,
+            rsa_password=request.rsa_password,
+            date_str=request.date_str
+        )
+        
+        stego_b64 = base64.b64encode(result.stego_image).decode('utf-8')
         day_of_week = get_day_from_date(result.date_used)
         
         return EncodeResponse(
@@ -217,16 +287,16 @@ async def api_encode(request: EncodeRequest):
 @app.post("/decode", response_model=DecodeResponse)
 async def api_decode(request: DecodeRequest):
     """
-    Decode a secret message from a stego image.
+    Decode a message or file from a stego image.
     
-    Images must be base64-encoded.
+    Returns payload_type to indicate if result is text or file.
     """
     try:
         stego = base64.b64decode(request.stego_image_base64)
         ref_photo = base64.b64decode(request.reference_photo_base64)
         rsa_key = base64.b64decode(request.rsa_key_base64) if request.rsa_key_base64 else None
         
-        message = decode(
+        result = decode(
             stego_image=stego,
             reference_photo=ref_photo,
             day_phrase=request.day_phrase,
@@ -235,7 +305,18 @@ async def api_decode(request: DecodeRequest):
             rsa_password=request.rsa_password
         )
         
-        return DecodeResponse(message=message)
+        if result.is_file:
+            return DecodeResponse(
+                payload_type='file',
+                file_data_base64=base64.b64encode(result.file_data).decode('utf-8'),
+                filename=result.filename,
+                mime_type=result.mime_type
+            )
+        else:
+            return DecodeResponse(
+                payload_type='text',
+                message=result.message
+            )
         
     except DecryptionError as e:
         raise HTTPException(401, "Decryption failed. Check credentials.")
@@ -247,10 +328,11 @@ async def api_decode(request: DecodeRequest):
 
 @app.post("/encode/multipart")
 async def api_encode_multipart(
-    message: str = Form(...),
     day_phrase: str = Form(...),
     reference_photo: UploadFile = File(...),
     carrier: UploadFile = File(...),
+    message: str = Form(""),
+    payload_file: Optional[UploadFile] = File(None),
     pin: str = Form(""),
     rsa_key: Optional[UploadFile] = File(None),
     rsa_password: str = Form(""),
@@ -259,6 +341,7 @@ async def api_encode_multipart(
     """
     Encode using multipart form data (file uploads).
     
+    Provide either 'message' (text) or 'payload_file' (binary file).
     Returns the stego image directly as PNG with metadata headers.
     """
     try:
@@ -266,8 +349,21 @@ async def api_encode_multipart(
         carrier_data = await carrier.read()
         rsa_key_data = await rsa_key.read() if rsa_key else None
         
+        # Determine payload
+        if payload_file and payload_file.filename:
+            file_data = await payload_file.read()
+            payload = FilePayload(
+                data=file_data,
+                filename=payload_file.filename,
+                mime_type=payload_file.content_type
+            )
+        elif message:
+            payload = message
+        else:
+            raise HTTPException(400, "Must provide either 'message' or 'payload_file'")
+        
         result = encode(
-            message=message,
+            message=payload,
             reference_photo=ref_data,
             carrier_image=carrier_data,
             day_phrase=day_phrase,
@@ -277,7 +373,6 @@ async def api_encode_multipart(
             date_str=date_str if date_str else None
         )
         
-        # Get day of week from the date used
         day_of_week = get_day_from_date(result.date_used)
         
         return Response(
@@ -310,13 +405,15 @@ async def api_decode_multipart(
 ):
     """
     Decode using multipart form data (file uploads).
+    
+    Returns JSON with payload_type indicating text or file.
     """
     try:
         ref_data = await reference_photo.read()
         stego_data = await stego_image.read()
         rsa_key_data = await rsa_key.read() if rsa_key else None
         
-        message = decode(
+        result = decode(
             stego_image=stego_data,
             reference_photo=ref_data,
             day_phrase=day_phrase,
@@ -325,7 +422,18 @@ async def api_decode_multipart(
             rsa_password=rsa_password if rsa_password else None
         )
         
-        return DecodeResponse(message=message)
+        if result.is_file:
+            return DecodeResponse(
+                payload_type='file',
+                file_data_base64=base64.b64encode(result.file_data).decode('utf-8'),
+                filename=result.filename,
+                mime_type=result.mime_type
+            )
+        else:
+            return DecodeResponse(
+                payload_type='text',
+                message=result.message
+            )
         
     except DecryptionError:
         raise HTTPException(401, "Decryption failed. Check credentials.")
diff --git a/frontends/cli/main.py b/frontends/cli/main.py
index 6cb80d2..a6a281a 100644
--- a/frontends/cli/main.py
+++ b/frontends/cli/main.py
@@ -20,12 +20,14 @@ sys.path.insert(0, str(Path(__file__).parent.parent.parent / 'src'))
 
 import stegasoo
 from stegasoo import (
-    encode, decode, generate_credentials,
+    encode, encode_file, decode,
+    generate_credentials,
     export_rsa_key_pem, load_rsa_key,
     validate_image, calculate_capacity,
     get_day_from_date, parse_date_from_filename,
     DAY_NAMES, __version__,
     StegasooError, DecryptionError, ExtractionError,
+    FilePayload,
 )
 
 
@@ -42,7 +44,7 @@ def cli():
     """
     Stegasoo - Secure steganography with hybrid authentication.
     
-    Hide encrypted messages in images using a combination of:
+    Hide encrypted messages or files in images using a combination of:
     
     \b
     • Reference photo (something you have)
@@ -170,8 +172,9 @@ def generate(pin, rsa, pin_length, rsa_bits, words, output, password, as_json):
 @cli.command()
 @click.option('--ref', '-r', required=True, type=click.Path(exists=True), help='Reference photo')
 @click.option('--carrier', '-c', required=True, type=click.Path(exists=True), help='Carrier image')
-@click.option('--message', '-m', help='Message to encode (or use stdin)')
-@click.option('--message-file', '-f', type=click.Path(exists=True), help='Read message from file')
+@click.option('--message', '-m', help='Text message to encode')
+@click.option('--message-file', '-f', type=click.Path(exists=True), help='Read text message from file')
+@click.option('--embed-file', '-e', type=click.Path(exists=True), help='Embed a file (binary)')
 @click.option('--phrase', '-p', required=True, help='Day phrase')
 @click.option('--pin', help='Static PIN')
 @click.option('--key', '-k', type=click.Path(exists=True), help='RSA key file')
@@ -179,28 +182,46 @@ def generate(pin, rsa, pin_length, rsa_bits, words, output, password, as_json):
 @click.option('--output', '-o', type=click.Path(), help='Output file (default: auto-generated)')
 @click.option('--date', 'date_str', help='Date override (YYYY-MM-DD)')
 @click.option('--quiet', '-q', is_flag=True, help='Suppress output except errors')
-def encode_cmd(ref, carrier, message, message_file, phrase, pin, key, key_password, output, date_str, quiet):
+def encode_cmd(ref, carrier, message, message_file, embed_file, phrase, pin, key, key_password, output, date_str, quiet):
     """
-    Encode a secret message into an image.
+    Encode a secret message or file into an image.
     
     Requires a reference photo, carrier image, and day phrase.
     Must provide either --pin or --key (or both).
     
+    For text messages, use -m or -f or pipe via stdin.
+    For binary files, use -e/--embed-file.
+    
     \b
     Examples:
+        # Text message
         stegasoo encode -r photo.jpg -c meme.png -p "apple forest thunder" --pin 123456 -m "secret"
-        echo "secret" | stegasoo encode -r photo.jpg -c meme.png -p "word1 word2 word3" --pin 123456
-        stegasoo encode -r photo.jpg -c meme.png -p "words" -k mykey.pem --key-password "pass"
+        
+        # Text from file
+        stegasoo encode -r photo.jpg -c meme.png -p "words" --pin 123456 -f message.txt
+        
+        # Embed a binary file (PDF, ZIP, etc.)
+        stegasoo encode -r photo.jpg -c meme.png -p "words" --pin 123456 -e secret.pdf
+        
+        # Pipe text
+        echo "secret" | stegasoo encode -r photo.jpg -c meme.png -p "words" --pin 123456
     """
-    # Get message
-    if message:
-        msg = message
+    # Determine what to encode
+    payload = None
+    
+    if embed_file:
+        # Binary file embedding
+        payload = FilePayload.from_file(embed_file)
+        if not quiet:
+            click.echo(f"Embedding file: {payload.filename} ({len(payload.data):,} bytes)")
+    elif message:
+        payload = message
     elif message_file:
-        msg = Path(message_file).read_text()
+        payload = Path(message_file).read_text()
     elif not sys.stdin.isatty():
-        msg = sys.stdin.read()
+        payload = sys.stdin.read()
     else:
-        raise click.UsageError("Must provide message via -m, -f, or stdin")
+        raise click.UsageError("Must provide message via -m, -f, -e, or stdin")
     
     # Load key if provided
     rsa_key_data = None
@@ -216,7 +237,7 @@ def encode_cmd(ref, carrier, message, message_file, phrase, pin, key, key_passwo
         carrier_image = Path(carrier).read_bytes()
         
         result = encode(
-            message=msg,
+            message=payload,
             reference_photo=ref_photo,
             carrier_image=carrier_image,
             day_phrase=phrase,
@@ -259,19 +280,26 @@ def encode_cmd(ref, carrier, message, message_file, phrase, pin, key, key_passwo
 @click.option('--pin', help='Static PIN')
 @click.option('--key', '-k', type=click.Path(exists=True), help='RSA key file')
 @click.option('--key-password', help='RSA key password')
-@click.option('--output', '-o', type=click.Path(), help='Save message to file')
-@click.option('--quiet', '-q', is_flag=True, help='Output only the message')
-def decode_cmd(ref, stego, phrase, pin, key, key_password, output, quiet):
+@click.option('--output', '-o', type=click.Path(), help='Save decoded content to file')
+@click.option('--quiet', '-q', is_flag=True, help='Output only the content (for text) or suppress messages (for files)')
+@click.option('--force', is_flag=True, help='Overwrite existing output file')
+def decode_cmd(ref, stego, phrase, pin, key, key_password, output, quiet, force):
     """
-    Decode a secret message from a stego image.
+    Decode a secret message or file from a stego image.
     
     Must use the same credentials that were used for encoding.
+    Automatically detects whether content is text or a file.
     
     \b
     Examples:
+        # Decode and print text
         stegasoo decode -r photo.jpg -s stego.png -p "apple forest thunder" --pin 123456
-        stegasoo decode -r photo.jpg -s stego.png -p "words" -k mykey.pem --key-password "pass"
-        stegasoo decode -r photo.jpg -s stego.png -p "words" --pin 123456 -o message.txt
+        
+        # Decode and save (auto-detect type)
+        stegasoo decode -r photo.jpg -s stego.png -p "words" --pin 123456 -o output.txt
+        
+        # Quiet mode for piping text
+        stegasoo decode -r photo.jpg -s stego.png -p "words" --pin 123456 -q | less
     """
     # Load key if provided
     rsa_key_data = None
@@ -286,7 +314,7 @@ def decode_cmd(ref, stego, phrase, pin, key, key_password, output, quiet):
         ref_photo = Path(ref).read_bytes()
         stego_image = Path(stego).read_bytes()
         
-        message = decode(
+        result = decode(
             stego_image=stego_image,
             reference_photo=ref_photo,
             day_phrase=phrase,
@@ -295,18 +323,42 @@ def decode_cmd(ref, stego, phrase, pin, key, key_password, output, quiet):
             rsa_password=key_password,
         )
         
-        if output:
-            Path(output).write_text(message)
-            if not quiet:
-                click.secho(f"✓ Decoded successfully!", fg='green')
-                click.echo(f"  Saved to: {output}")
-        else:
-            if quiet:
-                click.echo(message)
+        if result.is_file:
+            # File content
+            if output:
+                out_path = Path(output)
+            elif result.filename:
+                out_path = Path(result.filename)
             else:
-                click.secho("✓ Decoded successfully!", fg='green')
-                click.echo()
-                click.echo(message)
+                out_path = Path("decoded_file")
+            
+            if out_path.exists() and not force:
+                raise click.ClickException(
+                    f"Output file '{out_path}' exists. Use --force to overwrite."
+                )
+            
+            out_path.write_bytes(result.file_data)
+            
+            if not quiet:
+                click.secho("✓ Decoded file successfully!", fg='green')
+                click.echo(f"  Saved to: {out_path}")
+                click.echo(f"  Size: {len(result.file_data):,} bytes")
+                if result.mime_type:
+                    click.echo(f"  Type: {result.mime_type}")
+        else:
+            # Text content
+            if output:
+                Path(output).write_text(result.message)
+                if not quiet:
+                    click.secho("✓ Decoded successfully!", fg='green')
+                    click.echo(f"  Saved to: {output}")
+            else:
+                if quiet:
+                    click.echo(result.message)
+                else:
+                    click.secho("✓ Decoded successfully!", fg='green')
+                    click.echo()
+                    click.echo(result.message)
         
     except (DecryptionError, ExtractionError) as e:
         raise click.ClickException(f"Decryption failed: {e}")
diff --git a/frontends/web/app.py b/frontends/web/app.py
index f854d70..f12a2cf 100644
--- a/frontends/web/app.py
+++ b/frontends/web/app.py
@@ -3,13 +3,14 @@
 Stegasoo Web Frontend
 
 Flask-based web UI for steganography operations.
-This is a thin wrapper around the stegasoo library.
+Supports both text messages and file embedding.
 """
 
 import io
 import sys
 import time
 import secrets
+import mimetypes
 from pathlib import Path
 from datetime import datetime
 
@@ -27,14 +28,17 @@ from stegasoo import (
     export_rsa_key_pem, load_rsa_key,
     validate_pin, validate_message, validate_image,
     validate_rsa_key, validate_security_factors,
+    validate_file_payload,
     get_today_day, generate_filename,
     DAY_NAMES, __version__,
     StegasooError, DecryptionError, CapacityError,
     has_argon2,
+    FilePayload,
+    MAX_FILE_PAYLOAD_SIZE,
 )
 from stegasoo.constants import (
     MAX_MESSAGE_SIZE, MIN_PIN_LENGTH, MAX_PIN_LENGTH,
-    VALID_RSA_SIZES,
+    VALID_RSA_SIZES, MAX_FILE_SIZE,
 )
 
 
@@ -44,7 +48,7 @@ from stegasoo.constants import (
 
 app = Flask(__name__)
 app.secret_key = secrets.token_hex(32)
-app.config['MAX_CONTENT_LENGTH'] = 5 * 1024 * 1024  # 5MB max upload
+app.config['MAX_CONTENT_LENGTH'] = MAX_FILE_SIZE  # 10MB max upload
 
 # Temporary file storage for sharing (file_id -> {data, timestamp, filename})
 TEMP_FILES: dict[str, dict] = {}
@@ -67,6 +71,16 @@ def allowed_image(filename: str) -> bool:
     return ext in {'png', 'jpg', 'jpeg', 'bmp', 'gif'}
 
 
+def format_size(size_bytes: int) -> str:
+    """Format file size for display."""
+    if size_bytes < 1024:
+        return f"{size_bytes} B"
+    elif size_bytes < 1024 * 1024:
+        return f"{size_bytes / 1024:.1f} KB"
+    else:
+        return f"{size_bytes / (1024 * 1024):.1f} MB"
+
+
 # ============================================================================
 # ROUTES
 # ============================================================================
@@ -164,6 +178,7 @@ def download_key():
 @app.route('/encode', methods=['GET', 'POST'])
 def encode_page():
     day_of_week = get_today_day()
+    max_payload_kb = MAX_FILE_PAYLOAD_SIZE // 1024
     
     if request.method == 'POST':
         try:
@@ -171,30 +186,50 @@ def encode_page():
             ref_photo = request.files.get('reference_photo')
             carrier = request.files.get('carrier')
             rsa_key_file = request.files.get('rsa_key')
+            payload_file = request.files.get('payload_file')
             
             if not ref_photo or not carrier:
                 flash('Both reference photo and carrier image are required', 'error')
-                return render_template('encode.html', day_of_week=day_of_week)
+                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             if not allowed_image(ref_photo.filename) or not allowed_image(carrier.filename):
                 flash('Invalid file type. Use PNG, JPG, or BMP', 'error')
-                return render_template('encode.html', day_of_week=day_of_week)
+                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             # Get form data
             message = request.form.get('message', '')
             day_phrase = request.form.get('day_phrase', '')
             pin = request.form.get('pin', '').strip()
             rsa_password = request.form.get('rsa_password', '')
+            payload_type = request.form.get('payload_type', 'text')
             
-            # Validate message
-            result = validate_message(message)
-            if not result.is_valid:
-                flash(result.error_message, 'error')
-                return render_template('encode.html', day_of_week=day_of_week)
+            # Determine payload
+            if payload_type == 'file' and payload_file and payload_file.filename:
+                # File payload
+                file_data = payload_file.read()
+                
+                result = validate_file_payload(file_data, payload_file.filename)
+                if not result.is_valid:
+                    flash(result.error_message, 'error')
+                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
+                
+                mime_type, _ = mimetypes.guess_type(payload_file.filename)
+                payload = FilePayload(
+                    data=file_data,
+                    filename=payload_file.filename,
+                    mime_type=mime_type
+                )
+            else:
+                # Text message
+                result = validate_message(message)
+                if not result.is_valid:
+                    flash(result.error_message, 'error')
+                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
+                payload = message
             
             if not day_phrase:
                 flash('Day phrase is required', 'error')
-                return render_template('encode.html', day_of_week=day_of_week)
+                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             # Read files
             ref_data = ref_photo.read()
@@ -205,27 +240,27 @@ def encode_page():
             result = validate_security_factors(pin, rsa_key_data)
             if not result.is_valid:
                 flash(result.error_message, 'error')
-                return render_template('encode.html', day_of_week=day_of_week)
+                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             # Validate PIN if provided
             if pin:
                 result = validate_pin(pin)
                 if not result.is_valid:
                     flash(result.error_message, 'error')
-                    return render_template('encode.html', day_of_week=day_of_week)
+                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             # Validate RSA key if provided
             if rsa_key_data:
                 result = validate_rsa_key(rsa_key_data, rsa_password if rsa_password else None)
                 if not result.is_valid:
                     flash(result.error_message, 'error')
-                    return render_template('encode.html', day_of_week=day_of_week)
+                    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             # Validate carrier image
             result = validate_image(carrier_data, "Carrier image")
             if not result.is_valid:
                 flash(result.error_message, 'error')
-                return render_template('encode.html', day_of_week=day_of_week)
+                return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
             
             # Get date
             client_date = request.form.get('client_date', '').strip()
@@ -236,7 +271,7 @@ def encode_page():
             
             # Encode
             encode_result = encode(
-                message=message,
+                message=payload,
                 reference_photo=ref_data,
                 carrier_image=carrier_data,
                 day_phrase=day_phrase,
@@ -259,15 +294,15 @@ def encode_page():
             
         except CapacityError as e:
             flash(str(e), 'error')
-            return render_template('encode.html', day_of_week=day_of_week)
+            return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
         except StegasooError as e:
             flash(str(e), 'error')
-            return render_template('encode.html', day_of_week=day_of_week)
+            return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
         except Exception as e:
             flash(f'Error: {e}', 'error')
-            return render_template('encode.html', day_of_week=day_of_week)
+            return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
     
-    return render_template('encode.html', day_of_week=day_of_week)
+    return render_template('encode.html', day_of_week=day_of_week, max_payload_kb=max_payload_kb)
 
 
 @app.route('/encode/result/<file_id>')
@@ -299,7 +334,7 @@ def encode_download(file_id):
 
 
 @app.route('/encode/file/<file_id>')
-def encode_file(file_id):
+def encode_file_route(file_id):
     """Serve file for Web Share API."""
     if file_id not in TEMP_FILES:
         return "Not found", 404
@@ -368,7 +403,7 @@ def decode_page():
                     return render_template('decode.html')
             
             # Decode
-            message = decode(
+            decode_result = decode(
                 stego_image=stego_data,
                 reference_photo=ref_data,
                 day_phrase=day_phrase,
@@ -377,7 +412,29 @@ def decode_page():
                 rsa_password=rsa_password if rsa_password else None
             )
             
-            return render_template('decode.html', decoded_message=message)
+            if decode_result.is_file:
+                # File content - store temporarily for download
+                file_id = secrets.token_urlsafe(16)
+                cleanup_temp_files()
+                
+                filename = decode_result.filename or 'decoded_file'
+                TEMP_FILES[file_id] = {
+                    'data': decode_result.file_data,
+                    'filename': filename,
+                    'mime_type': decode_result.mime_type,
+                    'timestamp': time.time()
+                }
+                
+                return render_template('decode.html',
+                    decoded_file=True,
+                    file_id=file_id,
+                    filename=filename,
+                    file_size=format_size(len(decode_result.file_data)),
+                    mime_type=decode_result.mime_type
+                )
+            else:
+                # Text content
+                return render_template('decode.html', decoded_message=decode_result.message)
             
         except DecryptionError:
             flash('Decryption failed. Check your phrase, PIN, RSA key, and reference photo.', 'error')
@@ -392,9 +449,30 @@ def decode_page():
     return render_template('decode.html')
 
 
+@app.route('/decode/download/<file_id>')
+def decode_download(file_id):
+    """Download decoded file."""
+    if file_id not in TEMP_FILES:
+        flash('File expired or not found.', 'error')
+        return redirect(url_for('decode_page'))
+    
+    file_info = TEMP_FILES[file_id]
+    mime_type = file_info.get('mime_type', 'application/octet-stream')
+    
+    return send_file(
+        io.BytesIO(file_info['data']),
+        mimetype=mime_type,
+        as_attachment=True,
+        download_name=file_info['filename']
+    )
+
+
 @app.route('/about')
 def about():
-    return render_template('about.html', has_argon2=has_argon2())
+    return render_template('about.html', 
+        has_argon2=has_argon2(),
+        max_payload_kb=MAX_FILE_PAYLOAD_SIZE // 1024
+    )
 
 
 # ============================================================================
diff --git a/frontends/web/templates/decode.html b/frontends/web/templates/decode.html
index 237c83c..cfb28e6 100644
--- a/frontends/web/templates/decode.html
+++ b/frontends/web/templates/decode.html
@@ -7,10 +7,11 @@
     <div class="col-lg-8">
         <div class="card">
             <div class="card-header">
-                <h5 class="mb-0"><i class="bi bi-unlock-fill me-2"></i>Decode Secret Message</h5>
+                <h5 class="mb-0"><i class="bi bi-unlock-fill me-2"></i>Decode Secret Message or File</h5>
             </div>
             <div class="card-body">
                 {% if decoded_message %}
+                <!-- Text Message Result -->
                 <div class="alert alert-success">
                     <h6><i class="bi bi-check-circle me-2"></i>Message Decrypted Successfully!</h6>
                 </div>
@@ -23,17 +24,40 @@
                   </button>
                 </div>
 
-                i<!--then<div class="mb-4">
-                    <label class="form-label text-muted">Decoded Message:</label>
-                    <div class="alert-message">{{ decoded_message }}</div>
-                </div>-->
+                <a href="/decode" class="btn btn-outline-light w-100 mt-3">
+                    <i class="bi bi-arrow-repeat me-2"></i>Decode Another
+                </a>
+                
+                {% elif decoded_file %}
+                <!-- File Result -->
+                <div class="alert alert-success">
+                    <h6><i class="bi bi-check-circle me-2"></i>File Decrypted Successfully!</h6>
+                </div>
+                
+                <div class="text-center mb-4">
+                    <i class="bi bi-file-earmark-check text-success" style="font-size: 4rem;"></i>
+                    <h5 class="mt-3">{{ filename }}</h5>
+                    <p class="text-muted mb-1">{{ file_size }}</p>
+                    {% if mime_type %}
+                    <small class="text-muted">Type: {{ mime_type }}</small>
+                    {% endif %}
+                </div>
+                
+                <a href="{{ url_for('decode_download', file_id=file_id) }}" class="btn btn-primary btn-lg w-100 mb-3">
+                    <i class="bi bi-download me-2"></i>Download File
+                </a>
+                
+                <div class="alert alert-warning small">
+                    <i class="bi bi-clock me-1"></i>
+                    <strong>File expires in 5 minutes.</strong> Download now.
+                </div>
                 
                 <a href="/decode" class="btn btn-outline-light w-100">
-                    <i class="bi bi-arrow-repeat me-2"></i>Decode Another Message
+                    <i class="bi bi-arrow-repeat me-2"></i>Decode Another
                 </a>
                 
                 {% else %}
-                
+                <!-- Decode Form -->
                 <form method="POST" enctype="multipart/form-data" id="decodeForm">
                     <div class="row">
                         <div class="col-md-6 mb-3">
@@ -66,7 +90,7 @@
                                 <img class="drop-zone-preview d-none">
                             </div>
                             <div class="form-text">
-                                The image containing the hidden message
+                                The image containing the hidden message/file
                             </div>
                         </div>
                     </div>
@@ -130,7 +154,7 @@
                     </div>
                     
                     <button type="submit" class="btn btn-primary btn-lg w-100" id="decodeBtn">
-                        <i class="bi bi-unlock me-2"></i>Decode Message
+                        <i class="bi bi-unlock me-2"></i>Decode
                     </button>
                 </form>
                 
@@ -138,6 +162,7 @@
             </div>
         </div>
         
+        {% if not decoded_message and not decoded_file %}
         <div class="card mt-4">
             <div class="card-body">
                 <h6 class="text-muted mb-3"><i class="bi bi-question-circle me-2"></i>Troubleshooting</h6>
@@ -165,6 +190,7 @@
                 </ul>
             </div>
         </div>
+        {% endif %}
     </div>
 </div>
 {% endblock %}
@@ -209,7 +235,7 @@ function updateDayLabel(dayName) {
     }
 }
 
-// 1. PIN Toggle
+// PIN Toggle
 document.getElementById('togglePin')?.addEventListener('click', function() {
     const input = document.getElementById('pinInput');
     const icon = this.querySelector('i');
@@ -222,9 +248,8 @@ document.getElementById('togglePin')?.addEventListener('click', function() {
     }
 });
 
-// 2. Paste from Clipboard
+// Paste from Clipboard
 document.addEventListener('paste', function(e) {
-    // Only run if the form exists (we are not on the success page)
     if (!document.getElementById('decodeForm')) return;
 
     const items = e.clipboardData.items;
@@ -232,7 +257,6 @@ document.addEventListener('paste', function(e) {
         if (items[i].type.indexOf("image") !== -1) {
             const blob = items[i].getAsFile();
             
-            // Priority for Decode: Fill Stego Image first (most common), then Reference
             const stegoInput = document.querySelector('input[name="stego_image"]');
             const refInput = document.querySelector('input[name="reference_photo"]');
             
diff --git a/frontends/web/templates/encode.html b/frontends/web/templates/encode.html
index 5790eaa..a6b37f5 100644
--- a/frontends/web/templates/encode.html
+++ b/frontends/web/templates/encode.html
@@ -7,7 +7,7 @@
     <div class="col-lg-8">
         <div class="card">
             <div class="card-header">
-                <h5 class="mb-0"><i class="bi bi-lock-fill me-2"></i>Encode Secret Message</h5>
+                <h5 class="mb-0"><i class="bi bi-lock-fill me-2"></i>Encode Secret Message or File</h5>
             </div>
             <div class="card-body">
                 <form method="POST" enctype="multipart/form-data" id="encodeForm">
@@ -49,15 +49,34 @@
                         </div>
                     </div>
                     
+                    <!-- Payload Type Selector -->
                     <div class="mb-3">
+                        <label class="form-label">
+                            <i class="bi bi-box me-1"></i> What to Encode
+                        </label>
+                        <div class="btn-group w-100" role="group">
+                            <input type="radio" class="btn-check" name="payload_type" id="payloadText" value="text" checked>
+                            <label class="btn btn-outline-primary" for="payloadText">
+                                <i class="bi bi-chat-left-text me-1"></i> Text Message
+                            </label>
+                            
+                            <input type="radio" class="btn-check" name="payload_type" id="payloadFile" value="file">
+                            <label class="btn btn-outline-primary" for="payloadFile">
+                                <i class="bi bi-file-earmark me-1"></i> File
+                            </label>
+                        </div>
+                    </div>
+                    
+                    <!-- Text Message Input -->
+                    <div class="mb-3" id="textPayloadSection">
                         <label class="form-label">
                             <i class="bi bi-chat-left-text me-1"></i> Secret Message
                         </label>
                         <textarea name="message" class="form-control" rows="4" id="messageInput"
-                                  placeholder="Enter your secret message here..." required></textarea>
+                                  placeholder="Enter your secret message here..."></textarea>
                         <div class="d-flex justify-content-between form-text">
                             <span>
-                                <span id="charCount">0</span> / 50,000 characters
+                                <span id="charCount">0</span> / 250,000 characters
                                 <span id="charWarning" class="text-warning d-none ms-2">
                                     <i class="bi bi-exclamation-triangle"></i> Getting long!
                                 </span>
@@ -66,6 +85,29 @@
                         </div>
                     </div>
                     
+                    <!-- File Upload Input -->
+                    <div class="mb-3 d-none" id="filePayloadSection">
+                        <label class="form-label">
+                            <i class="bi bi-file-earmark me-1"></i> File to Embed
+                        </label>
+                        <div class="drop-zone" id="payloadDropZone">
+                            <input type="file" name="payload_file" id="payloadFileInput">
+                            <div class="drop-zone-label" id="payloadDropLabel">
+                                <i class="bi bi-cloud-arrow-up fs-3 d-block mb-2 text-muted"></i>
+                                <span class="text-muted">Drop any file or click to browse</span>
+                                <div class="small text-muted mt-1">Max {{ max_payload_kb }} KB</div>
+                            </div>
+                        </div>
+                        <div class="form-text">
+                            Supports any file type: PDF, ZIP, documents, etc.
+                        </div>
+                        <div id="fileInfo" class="d-none mt-2 p-2 bg-dark rounded">
+                            <i class="bi bi-file-earmark-check text-success me-2"></i>
+                            <span id="fileInfoName"></span>
+                            <span class="text-muted">(<span id="fileInfoSize"></span>)</span>
+                        </div>
+                    </div>
+                    
                     <div class="mb-3">
                         <label class="form-label" id="dayPhraseLabel">
                             <i class="bi bi-chat-quote me-1"></i> {{ day_of_week }}'s Phrase
@@ -121,7 +163,7 @@
                     </div>
                     
                     <button type="submit" class="btn btn-primary btn-lg w-100" id="encodeBtn">
-                        <i class="bi bi-lock me-2"></i>Encode Message
+                        <i class="bi bi-lock me-2"></i>Encode
                     </button>
                 </form>
                 
@@ -146,8 +188,8 @@
                     <i class="bi bi-info-circle me-1"></i>
                     <strong>Limits:</strong> 
                     Carrier image max ~4 megapixels (2000×2000). 
-                    Files max 5MB each. 
-                    Message max 50KB.
+                    Files max 10MB upload. 
+                    Payload max {{ max_payload_kb }} KB.
                 </div>
             </div>
         </div>
@@ -177,6 +219,57 @@ if (dateInput) {
     dateInput.value = localDate;
 }
 
+// Payload type switching
+const payloadTextRadio = document.getElementById('payloadText');
+const payloadFileRadio = document.getElementById('payloadFile');
+const textSection = document.getElementById('textPayloadSection');
+const fileSection = document.getElementById('filePayloadSection');
+const messageInput = document.getElementById('messageInput');
+const payloadFileInput = document.getElementById('payloadFileInput');
+
+function updatePayloadSection() {
+    const isText = payloadTextRadio.checked;
+    textSection.classList.toggle('d-none', !isText);
+    fileSection.classList.toggle('d-none', isText);
+    
+    // Update required attribute
+    if (isText) {
+        messageInput.required = true;
+        payloadFileInput.required = false;
+    } else {
+        messageInput.required = false;
+        payloadFileInput.required = true;
+    }
+}
+
+payloadTextRadio.addEventListener('change', updatePayloadSection);
+payloadFileRadio.addEventListener('change', updatePayloadSection);
+
+// File payload info display
+const fileInfo = document.getElementById('fileInfo');
+const fileInfoName = document.getElementById('fileInfoName');
+const fileInfoSize = document.getElementById('fileInfoSize');
+const payloadDropLabel = document.getElementById('payloadDropLabel');
+
+payloadFileInput.addEventListener('change', function() {
+    if (this.files && this.files[0]) {
+        const file = this.files[0];
+        fileInfoName.textContent = file.name;
+        fileInfoSize.textContent = formatFileSize(file.size);
+        fileInfo.classList.remove('d-none');
+        payloadDropLabel.innerHTML = `<i class="bi bi-check-circle text-success fs-3 d-block mb-2"></i><span>${file.name}</span>`;
+    } else {
+        fileInfo.classList.add('d-none');
+        payloadDropLabel.innerHTML = `<i class="bi bi-cloud-arrow-up fs-3 d-block mb-2 text-muted"></i><span class="text-muted">Drop any file or click to browse</span><div class="small text-muted mt-1">Max {{ max_payload_kb }} KB</div>`;
+    }
+});
+
+function formatFileSize(bytes) {
+    if (bytes < 1024) return bytes + ' B';
+    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
+    return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
+}
+
 // Show RSA password field when key is selected
 const rsaKeyInput = document.getElementById('rsaKeyInput');
 const rsaPasswordGroup = document.getElementById('rsaPasswordGroup');
@@ -192,12 +285,11 @@ document.getElementById('encodeForm').addEventListener('submit', function(e) {
     btn.disabled = true;
 });
 
-// Character counter
-const messageInput = document.getElementById('messageInput');
+// Character counter for text
 const charCount = document.getElementById('charCount');
 const charWarning = document.getElementById('charWarning');
 const charPercent = document.getElementById('charPercent');
-const maxChars = 50000;
+const maxChars = 250000;
 
 messageInput.addEventListener('input', function() {
     const len = this.value.length;
@@ -210,11 +302,12 @@ messageInput.addEventListener('input', function() {
     charCount.classList.toggle('text-danger', len > maxChars * 0.95);
 });
 
-// Drag & drop with preview
+// Drag & drop with preview for images
 document.querySelectorAll('.drop-zone').forEach(zone => {
     const input = zone.querySelector('input[type="file"]');
     const label = zone.querySelector('.drop-zone-label');
     const preview = zone.querySelector('.drop-zone-preview');
+    const isPayloadZone = zone.id === 'payloadDropZone';
     
     ['dragenter', 'dragover'].forEach(evt => {
         zone.addEventListener(evt, e => {
@@ -233,29 +326,38 @@ document.querySelectorAll('.drop-zone').forEach(zone => {
     zone.addEventListener('drop', e => {
         if (e.dataTransfer.files.length) {
             input.files = e.dataTransfer.files;
-            showPreview(e.dataTransfer.files[0]);
+            input.dispatchEvent(new Event('change'));
+            
+            if (!isPayloadZone) {
+                showPreview(e.dataTransfer.files[0]);
+            }
         }
     });
     
-    input.addEventListener('change', function() {
-        if (this.files && this.files[0]) {
-            showPreview(this.files[0]);
-        }
-    });
+    if (!isPayloadZone) {
+        input.addEventListener('change', function() {
+            if (this.files && this.files[0]) {
+                showPreview(this.files[0]);
+            }
+        });
+    }
     
     function showPreview(file) {
         if (!file.type.startsWith('image/')) return;
         
         const reader = new FileReader();
         reader.onload = e => {
-            preview.src = e.target.result;
-            preview.classList.remove('d-none');
+            if (preview) {
+                preview.src = e.target.result;
+                preview.classList.remove('d-none');
+            }
             label.innerHTML = '<i class="bi bi-check-circle text-success me-1"></i>' + file.name;
         };
         reader.readAsDataURL(file);
     }
 });
-// 1. PIN Toggle Logic
+
+// PIN Toggle Logic
 document.getElementById('togglePin').addEventListener('click', function() {
     const input = document.getElementById('pinInput');
     const icon = this.querySelector('i');
@@ -268,17 +370,16 @@ document.getElementById('togglePin').addEventListener('click', function() {
     }
 });
 
-// 2. Prevent Same File Selection
+// Prevent Same File Selection
 function checkDuplicateFiles() {
     const refInput = document.querySelector('input[name="reference_photo"]');
     const carInput = document.querySelector('input[name="carrier"]');
     
     if (refInput.files[0] && carInput.files[0]) {
-        // Compare name and size as a proxy for identical files
         if (refInput.files[0].name === carInput.files[0].name && 
             refInput.files[0].size === carInput.files[0].size) {
             alert("Security Warning: You cannot use the same image for both Reference and Carrier!");
-            carInput.value = ''; // Clear carrier
+            carInput.value = '';
             document.getElementById('carrierPreview').classList.add('d-none');
             document.querySelector('#carrierDropZone .drop-zone-label').innerHTML = 
                 '<i class="bi bi-cloud-arrow-up fs-3 d-block mb-2 text-muted"></i>' +
@@ -289,14 +390,13 @@ function checkDuplicateFiles() {
 document.querySelector('input[name="reference_photo"]').addEventListener('change', checkDuplicateFiles);
 document.querySelector('input[name="carrier"]').addEventListener('change', checkDuplicateFiles);
 
-// 3. Paste from Clipboard
+// Paste from Clipboard
 document.addEventListener('paste', function(e) {
     const items = e.clipboardData.items;
     for (let i = 0; i < items.length; i++) {
         if (items[i].type.indexOf("image") !== -1) {
             const blob = items[i].getAsFile();
             
-            // Priority: Fill Carrier first, if empty. Else fill Reference.
             const carrierInput = document.querySelector('input[name="carrier"]');
             const refInput = document.querySelector('input[name="reference_photo"]');
             
@@ -307,7 +407,7 @@ document.addEventListener('paste', function(e) {
             targetInput.files = container.files;
             
             targetInput.dispatchEvent(new Event('change'));
-            break; // Only paste one image at a time
+            break;
         }
     }
 });
diff --git a/src/stegasoo/__init__.py b/src/stegasoo/__init__.py
index 9b5af30..b97cedd 100644
--- a/src/stegasoo/__init__.py
+++ b/src/stegasoo/__init__.py
@@ -1,10 +1,10 @@
 """
 Stegasoo - Secure Steganography Library
 
-A Python library for hiding encrypted messages in images using
+A Python library for hiding encrypted messages and files in images using
 hybrid photo + passphrase + PIN authentication.
 
-Basic Usage:
+Basic Usage - Text Message:
     from stegasoo import encode, decode, generate_credentials
     
     # Generate credentials
@@ -30,16 +30,36 @@ Basic Usage:
         f.write(result.stego_image)
     
     # Decode a message
-    message = decode(
+    decoded = decode(
         stego_image=result.stego_image,
         reference_photo=ref_photo,
         day_phrase="apple forest thunder",
         pin="123456"
     )
-    print(message)  # "Meet at midnight"
+    print(decoded.message)  # "Meet at midnight"
+
+File Embedding:
+    from stegasoo import encode_file, decode, FilePayload
+    
+    # Encode a file
+    result = encode_file(
+        filepath="secret_document.pdf",
+        reference_photo=ref_photo,
+        carrier_image=carrier,
+        day_phrase="apple forest thunder",
+        pin="123456"
+    )
+    
+    # Decode - automatically detects file vs text
+    decoded = decode(...)
+    if decoded.is_file:
+        with open(decoded.filename, 'wb') as f:
+            f.write(decoded.file_data)
+    else:
+        print(decoded.message)
 """
 
-from .constants import __version__, DAY_NAMES
+from .constants import __version__, DAY_NAMES, MAX_MESSAGE_SIZE, MAX_FILE_PAYLOAD_SIZE
 from .models import (
     Credentials,
     EncodeInput,
@@ -49,6 +69,7 @@ from .models import (
     EmbedStats,
     KeyInfo,
     ValidationResult,
+    FilePayload,
 )
 from .exceptions import (
     StegasooError,
@@ -83,6 +104,8 @@ from .keygen import (
 from .validation import (
     validate_pin,
     validate_message,
+    validate_payload,
+    validate_file_payload,
     validate_image,
     validate_rsa_key,
     validate_security_factors,
@@ -90,6 +113,7 @@ from .validation import (
     validate_date_string,
     require_valid_pin,
     require_valid_message,
+    require_valid_payload,
     require_valid_image,
     require_valid_rsa_key,
     require_security_factors,
@@ -97,6 +121,7 @@ from .validation import (
 from .crypto import (
     encrypt_message,
     decrypt_message,
+    decrypt_message_text,
     derive_hybrid_key,
     derive_pixel_key,
     hash_photo,
@@ -109,6 +134,9 @@ from .steganography import (
     extract_from_image,
     calculate_capacity,
     get_image_dimensions,
+    get_image_format,
+    is_lossless_format,
+    LOSSLESS_FORMATS,
 )
 from .utils import (
     generate_filename,
@@ -122,11 +150,12 @@ from .utils import (
 )
 
 from datetime import date
-from typing import Optional
+from pathlib import Path
+from typing import Optional, Union
 
 
 def encode(
-    message: str,
+    message: Union[str, bytes, FilePayload],
     reference_photo: bytes,
     carrier_image: bytes,
     day_phrase: str,
@@ -134,15 +163,16 @@ def encode(
     rsa_key_data: Optional[bytes] = None,
     rsa_password: Optional[str] = None,
     date_str: Optional[str] = None,
+    output_format: Optional[str] = None,
 ) -> EncodeResult:
     """
-    Encode a secret message into an image.
+    Encode a secret message or file into an image.
     
     High-level convenience function that handles validation,
     encryption, and embedding in one call.
     
     Args:
-        message: Secret message to hide
+        message: Secret message (str), raw bytes, or FilePayload to hide
         reference_photo: Shared reference photo bytes
         carrier_image: Image to hide message in
         day_phrase: Today's passphrase
@@ -150,6 +180,8 @@ def encode(
         rsa_key_data: RSA private key PEM bytes (optional if using PIN)
         rsa_password: Password for RSA key if encrypted
         date_str: Date string YYYY-MM-DD (defaults to today)
+        output_format: Force output format ('PNG', 'BMP'). If None, preserves
+                       carrier format for lossless types, defaults to PNG for lossy.
         
     Returns:
         EncodeResult with stego image and metadata
@@ -159,9 +191,13 @@ def encode(
         SecurityFactorError: If no PIN or RSA key provided
         CapacityError: If carrier is too small
         EncryptionError: If encryption fails
+        
+    Note:
+        Output format is always lossless (PNG or BMP) to preserve hidden data.
+        If carrier is JPEG/GIF, output will be PNG to maintain data integrity.
     """
     # Validate inputs
-    require_valid_message(message)
+    require_valid_payload(message)
     require_valid_image(carrier_image, "Carrier image")
     require_security_factors(pin, rsa_key_data)
     
@@ -174,7 +210,7 @@ def encode(
     if date_str is None:
         date_str = date.today().isoformat()
     
-    # Encrypt message
+    # Encrypt message/file
     encrypted = encrypt_message(
         message, reference_photo, day_phrase, date_str, pin, rsa_key_data
     )
@@ -184,11 +220,13 @@ def encode(
         reference_photo, day_phrase, date_str, pin, rsa_key_data
     )
     
-    # Embed in image
-    stego_data, stats = embed_in_image(carrier_image, encrypted, pixel_key)
+    # Embed in image (returns extension too)
+    stego_data, stats, extension = embed_in_image(
+        carrier_image, encrypted, pixel_key, output_format=output_format
+    )
     
-    # Generate filename
-    filename = generate_filename(date_str)
+    # Generate filename with correct extension
+    filename = generate_filename(date_str, extension=extension)
     
     return EncodeResult(
         stego_image=stego_data,
@@ -200,6 +238,102 @@ def encode(
     )
 
 
+def encode_file(
+    filepath: Union[str, Path],
+    reference_photo: bytes,
+    carrier_image: bytes,
+    day_phrase: str,
+    pin: str = "",
+    rsa_key_data: Optional[bytes] = None,
+    rsa_password: Optional[str] = None,
+    date_str: Optional[str] = None,
+    output_format: Optional[str] = None,
+    filename_override: Optional[str] = None,
+) -> EncodeResult:
+    """
+    Encode a file into an image.
+    
+    Convenience function for embedding files. Preserves original filename.
+    
+    Args:
+        filepath: Path to file to embed
+        reference_photo: Shared reference photo bytes
+        carrier_image: Image to hide file in
+        day_phrase: Today's passphrase
+        pin: Static PIN (optional if using RSA key)
+        rsa_key_data: RSA private key PEM bytes (optional if using PIN)
+        rsa_password: Password for RSA key if encrypted
+        date_str: Date string YYYY-MM-DD (defaults to today)
+        output_format: Force output format ('PNG', 'BMP')
+        filename_override: Override the stored filename
+        
+    Returns:
+        EncodeResult with stego image and metadata
+    """
+    payload = FilePayload.from_file(str(filepath), filename_override)
+    
+    return encode(
+        message=payload,
+        reference_photo=reference_photo,
+        carrier_image=carrier_image,
+        day_phrase=day_phrase,
+        pin=pin,
+        rsa_key_data=rsa_key_data,
+        rsa_password=rsa_password,
+        date_str=date_str,
+        output_format=output_format,
+    )
+
+
+def encode_bytes(
+    data: bytes,
+    filename: str,
+    reference_photo: bytes,
+    carrier_image: bytes,
+    day_phrase: str,
+    pin: str = "",
+    rsa_key_data: Optional[bytes] = None,
+    rsa_password: Optional[str] = None,
+    date_str: Optional[str] = None,
+    output_format: Optional[str] = None,
+    mime_type: Optional[str] = None,
+) -> EncodeResult:
+    """
+    Encode raw bytes with a filename into an image.
+    
+    Convenience function for embedding binary data with metadata.
+    
+    Args:
+        data: Raw bytes to embed
+        filename: Filename to associate with the data
+        reference_photo: Shared reference photo bytes
+        carrier_image: Image to hide data in
+        day_phrase: Today's passphrase
+        pin: Static PIN (optional if using RSA key)
+        rsa_key_data: RSA private key PEM bytes (optional if using PIN)
+        rsa_password: Password for RSA key if encrypted
+        date_str: Date string YYYY-MM-DD (defaults to today)
+        output_format: Force output format ('PNG', 'BMP')
+        mime_type: MIME type of the data
+        
+    Returns:
+        EncodeResult with stego image and metadata
+    """
+    payload = FilePayload(data=data, filename=filename, mime_type=mime_type)
+    
+    return encode(
+        message=payload,
+        reference_photo=reference_photo,
+        carrier_image=carrier_image,
+        day_phrase=day_phrase,
+        pin=pin,
+        rsa_key_data=rsa_key_data,
+        rsa_password=rsa_password,
+        date_str=date_str,
+        output_format=output_format,
+    )
+
+
 def decode(
     stego_image: bytes,
     reference_photo: bytes,
@@ -207,15 +341,15 @@ def decode(
     pin: str = "",
     rsa_key_data: Optional[bytes] = None,
     rsa_password: Optional[str] = None,
-) -> str:
+) -> DecodeResult:
     """
-    Decode a secret message from a stego image.
+    Decode a secret message or file from a stego image.
     
     High-level convenience function that handles extraction
     and decryption in one call.
     
     Args:
-        stego_image: Image containing hidden message
+        stego_image: Image containing hidden message/file
         reference_photo: Shared reference photo bytes
         day_phrase: Passphrase for the day message was encoded
         pin: Static PIN (if used during encoding)
@@ -223,7 +357,12 @@ def decode(
         rsa_password: Password for RSA key if encrypted
         
     Returns:
-        Decrypted message string
+        DecodeResult with:
+        - .payload_type: 'text' or 'file'
+        - .message: Decoded text (if text)
+        - .file_data: Decoded bytes (if file)
+        - .filename: Original filename (if file)
+        - .is_text / .is_file: Convenience properties
         
     Raises:
         ValidationError: If inputs are invalid
@@ -260,21 +399,72 @@ def decode(
     if not encrypted:
         raise ExtractionError("Could not extract data. Check your inputs.")
     
-    # Decrypt
+    # Decrypt and return full result
     return decrypt_message(encrypted, reference_photo, day_phrase, pin, rsa_key_data)
 
 
+def decode_text(
+    stego_image: bytes,
+    reference_photo: bytes,
+    day_phrase: str,
+    pin: str = "",
+    rsa_key_data: Optional[bytes] = None,
+    rsa_password: Optional[str] = None,
+) -> str:
+    """
+    Decode a text message from a stego image.
+    
+    Convenience function that returns just the text string.
+    Raises an error if the content is a binary file.
+    
+    Args:
+        stego_image: Image containing hidden message
+        reference_photo: Shared reference photo bytes
+        day_phrase: Passphrase for the day message was encoded
+        pin: Static PIN (if used during encoding)
+        rsa_key_data: RSA private key PEM bytes (if used during encoding)
+        rsa_password: Password for RSA key if encrypted
+        
+    Returns:
+        Decrypted message string
+        
+    Raises:
+        DecryptionError: If content is a binary file, not text
+    """
+    result = decode(stego_image, reference_photo, day_phrase, pin, rsa_key_data, rsa_password)
+    
+    if result.is_file:
+        # Try to decode file as text
+        if result.file_data:
+            try:
+                return result.file_data.decode('utf-8')
+            except UnicodeDecodeError:
+                raise DecryptionError(
+                    f"Content is a binary file ({result.filename or 'unnamed'}), not text. "
+                    "Use decode() instead and check result.is_file."
+                )
+        return ""
+    
+    return result.message or ""
+
+
 __all__ = [
     # Version
     '__version__',
     
     # High-level API
     'encode',
+    'encode_file',
+    'encode_bytes',
     'decode',
+    'decode_text',
     'generate_credentials',
     
     # Constants
     'DAY_NAMES',
+    'LOSSLESS_FORMATS',
+    'MAX_MESSAGE_SIZE',
+    'MAX_FILE_PAYLOAD_SIZE',
     
     # Models
     'Credentials',
@@ -285,6 +475,7 @@ __all__ = [
     'EmbedStats',
     'KeyInfo',
     'ValidationResult',
+    'FilePayload',
     
     # Exceptions
     'StegasooError',
@@ -318,6 +509,8 @@ __all__ = [
     # Validation
     'validate_pin',
     'validate_message',
+    'validate_payload',
+    'validate_file_payload',
     'validate_image',
     'validate_rsa_key',
     'validate_security_factors',
@@ -325,6 +518,7 @@ __all__ = [
     'validate_date_string',
     'require_valid_pin',
     'require_valid_message',
+    'require_valid_payload',
     'require_valid_image',
     'require_valid_rsa_key',
     'require_security_factors',
@@ -332,6 +526,7 @@ __all__ = [
     # Crypto
     'encrypt_message',
     'decrypt_message',
+    'decrypt_message_text',
     'derive_hybrid_key',
     'derive_pixel_key',
     'hash_photo',
@@ -344,6 +539,8 @@ __all__ = [
     'extract_from_image',
     'calculate_capacity',
     'get_image_dimensions',
+    'get_image_format',
+    'is_lossless_format',
     
     # Utilities
     'generate_filename',
diff --git a/src/stegasoo/constants.py b/src/stegasoo/constants.py
index 87cf449..b28364a 100644
--- a/src/stegasoo/constants.py
+++ b/src/stegasoo/constants.py
@@ -11,7 +11,7 @@ from pathlib import Path
 # VERSION
 # ============================================================================
 
-__version__ = "2.0.1"
+__version__ = "2.1.1"
 
 # ============================================================================
 # FILE FORMAT
@@ -20,6 +20,10 @@ __version__ = "2.0.1"
 MAGIC_HEADER = b'\x89ST3'
 FORMAT_VERSION = 3
 
+# Payload type markers
+PAYLOAD_TEXT = 0x01
+PAYLOAD_FILE = 0x02
+
 # ============================================================================
 # CRYPTO PARAMETERS
 # ============================================================================
@@ -40,9 +44,11 @@ PBKDF2_ITERATIONS = 600000
 # INPUT LIMITS
 # ============================================================================
 
-MAX_IMAGE_PIXELS = 4_000_000      # ~4 megapixels (2000x2000)
-MAX_MESSAGE_SIZE = 50_000         # 50 KB
-MAX_FILE_SIZE = 5 * 1024 * 1024   # 5 MB
+MAX_IMAGE_PIXELS = 16_000_000     # ~16 megapixels (4000x4000)
+MAX_MESSAGE_SIZE = 250_000        # 250 KB (text messages)
+MAX_FILE_PAYLOAD_SIZE = 250_000   # 250 KB (file payloads)
+MAX_FILENAME_LENGTH = 255         # Max filename length to store
+MAX_FILE_SIZE = 10 * 1024 * 1024  # 10 MB (upload limit)
 
 MIN_PIN_LENGTH = 6
 MAX_PIN_LENGTH = 9
@@ -78,11 +84,17 @@ DAY_NAMES = ('Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday',
 def get_data_dir() -> Path:
     """Get the data directory path."""
     # Check multiple locations
+    # From src/stegasoo/constants.py:
+    #   .parent = src/stegasoo/
+    #   .parent.parent = src/
+    #   .parent.parent.parent = project root (where data/ lives)
     candidates = [
-        Path(__file__).parent.parent.parent/ 'data',           # Development
+        Path(__file__).parent.parent.parent / 'data',          # Development: src/stegasoo -> project root
         Path(__file__).parent / 'data',                        # Installed package
         Path('/app/data'),                                     # Docker
         Path.cwd() / 'data',                                   # Current directory
+        Path.cwd().parent / 'data',                            # One level up from cwd
+        Path.cwd().parent.parent / 'data',                     # Two levels up from cwd
     ]
     
     for path in candidates:
diff --git a/src/stegasoo/crypto.py b/src/stegasoo/crypto.py
index 43ae47c..15aa98f 100644
--- a/src/stegasoo/crypto.py
+++ b/src/stegasoo/crypto.py
@@ -2,13 +2,15 @@
 Stegasoo Cryptographic Functions
 
 Key derivation, encryption, and decryption using AES-256-GCM.
+Supports both text messages and binary file payloads.
 """
 
 import io
 import hashlib
 import secrets
 import struct
-from typing import Optional
+import json
+from typing import Optional, Union
 
 from PIL import Image
 from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
@@ -19,7 +21,10 @@ from .constants import (
     SALT_SIZE, IV_SIZE, TAG_SIZE,
     ARGON2_TIME_COST, ARGON2_MEMORY_COST, ARGON2_PARALLELISM,
     PBKDF2_ITERATIONS,
+    PAYLOAD_TEXT, PAYLOAD_FILE,
+    MAX_FILENAME_LENGTH,
 )
+from .models import FilePayload, DecodeResult
 from .exceptions import (
     EncryptionError, DecryptionError, KeyDerivationError, InvalidHeaderError
 )
@@ -171,8 +176,112 @@ def derive_pixel_key(
     return hashlib.sha256(material + b"pixel_selection").digest()
 
 
+def _pack_payload(
+    content: Union[str, bytes, FilePayload],
+) -> tuple[bytes, int]:
+    """
+    Pack payload with type marker and metadata.
+    
+    Format for text:
+        [type:1][data]
+        
+    Format for file:
+        [type:1][filename_len:2][filename][mime_len:2][mime][data]
+    
+    Args:
+        content: Text string, raw bytes, or FilePayload
+        
+    Returns:
+        Tuple of (packed bytes, payload type)
+    """
+    if isinstance(content, str):
+        # Text message
+        data = content.encode('utf-8')
+        return bytes([PAYLOAD_TEXT]) + data, PAYLOAD_TEXT
+    
+    elif isinstance(content, FilePayload):
+        # File with metadata
+        filename = content.filename[:MAX_FILENAME_LENGTH].encode('utf-8')
+        mime = (content.mime_type or '')[:100].encode('utf-8')
+        
+        packed = (
+            bytes([PAYLOAD_FILE]) +
+            struct.pack('>H', len(filename)) +
+            filename +
+            struct.pack('>H', len(mime)) +
+            mime +
+            content.data
+        )
+        return packed, PAYLOAD_FILE
+    
+    else:
+        # Raw bytes - treat as file with no name
+        packed = (
+            bytes([PAYLOAD_FILE]) +
+            struct.pack('>H', 0) +  # No filename
+            struct.pack('>H', 0) +  # No mime
+            content
+        )
+        return packed, PAYLOAD_FILE
+
+
+def _unpack_payload(data: bytes) -> DecodeResult:
+    """
+    Unpack payload and extract content with metadata.
+    
+    Args:
+        data: Packed payload bytes
+        
+    Returns:
+        DecodeResult with appropriate content
+    """
+    if len(data) < 1:
+        raise DecryptionError("Empty payload")
+    
+    payload_type = data[0]
+    
+    if payload_type == PAYLOAD_TEXT:
+        # Text message
+        text = data[1:].decode('utf-8')
+        return DecodeResult(payload_type='text', message=text)
+    
+    elif payload_type == PAYLOAD_FILE:
+        # File with metadata
+        offset = 1
+        
+        # Read filename
+        filename_len = struct.unpack('>H', data[offset:offset+2])[0]
+        offset += 2
+        filename = data[offset:offset+filename_len].decode('utf-8') if filename_len else None
+        offset += filename_len
+        
+        # Read mime type
+        mime_len = struct.unpack('>H', data[offset:offset+2])[0]
+        offset += 2
+        mime_type = data[offset:offset+mime_len].decode('utf-8') if mime_len else None
+        offset += mime_len
+        
+        # Rest is file data
+        file_data = data[offset:]
+        
+        return DecodeResult(
+            payload_type='file',
+            file_data=file_data,
+            filename=filename,
+            mime_type=mime_type
+        )
+    
+    else:
+        # Unknown type - try to decode as text (backward compatibility)
+        try:
+            text = data.decode('utf-8')
+            return DecodeResult(payload_type='text', message=text)
+        except UnicodeDecodeError:
+            return DecodeResult(payload_type='file', file_data=data)
+
+
 def encrypt_message(
-    message: str | bytes,
+    message: Union[str, bytes, FilePayload],
     photo_data: bytes,
     day_phrase: str,
     date_str: str,
@@ -180,7 +289,7 @@ def encrypt_message(
     rsa_key_data: Optional[bytes] = None
 ) -> bytes:
     """
-    Encrypt message using AES-256-GCM with hybrid key derivation.
+    Encrypt message or file using AES-256-GCM with hybrid key derivation.
     
     Message format:
     - Magic header (4 bytes)
@@ -193,7 +302,7 @@ def encrypt_message(
     - Ciphertext (variable, padded)
     
     Args:
-        message: Message to encrypt
+        message: Message string, raw bytes, or FilePayload to encrypt
         photo_data: Reference photo bytes
         day_phrase: The day's phrase
         date_str: Date string (YYYY-MM-DD)
@@ -211,15 +320,15 @@ def encrypt_message(
         key = derive_hybrid_key(photo_data, day_phrase, date_str, salt, pin, rsa_key_data)
         iv = secrets.token_bytes(IV_SIZE)
         
-        if isinstance(message, str):
-            message = message.encode('utf-8')
+        # Pack payload with type marker
+        packed_payload, _ = _pack_payload(message)
         
         # Random padding to hide message length
         padding_len = secrets.randbelow(256) + 64
-        padded_len = ((len(message) + padding_len + 255) // 256) * 256
-        padding_needed = padded_len - len(message)
-        padding = secrets.token_bytes(padding_needed - 4) + struct.pack('>I', len(message))
-        padded_message = message + padding
+        padded_len = ((len(packed_payload) + padding_len + 255) // 256) * 256
+        padding_needed = padded_len - len(packed_payload)
+        padding = secrets.token_bytes(padding_needed - 4) + struct.pack('>I', len(packed_payload))
+        padded_message = packed_payload + padding
         
         # Encrypt with AES-256-GCM
         cipher = Cipher(algorithms.AES(key), modes.GCM(iv), backend=default_backend())
@@ -291,7 +400,7 @@ def decrypt_message(
     day_phrase: str,
     pin: str = "",
     rsa_key_data: Optional[bytes] = None
-) -> str:
+) -> DecodeResult:
     """
     Decrypt message using the embedded date from the header.
     
@@ -303,7 +412,7 @@ def decrypt_message(
         rsa_key_data: Optional RSA key bytes
         
     Returns:
-        Decrypted message string
+        DecodeResult with decrypted content
         
     Raises:
         InvalidHeaderError: If data doesn't have valid Stegasoo header
@@ -329,7 +438,11 @@ def decrypt_message(
         padded_plaintext = decryptor.update(header['ciphertext']) + decryptor.finalize()
         original_length = struct.unpack('>I', padded_plaintext[-4:])[0]
         
-        return padded_plaintext[:original_length].decode('utf-8')
+        payload_data = padded_plaintext[:original_length]
+        result = _unpack_payload(payload_data)
+        result.date_encoded = header['date']
+        
+        return result
         
     except Exception as e:
         raise DecryptionError(
@@ -337,6 +450,47 @@ def decrypt_message(
         ) from e
 
 
+def decrypt_message_text(
+    encrypted_data: bytes,
+    photo_data: bytes,
+    day_phrase: str,
+    pin: str = "",
+    rsa_key_data: Optional[bytes] = None
+) -> str:
+    """
+    Decrypt message and return as text string.
+    
+    For backward compatibility - returns text content or raises error for files.
+    
+    Args:
+        encrypted_data: Encrypted message bytes
+        photo_data: Reference photo bytes
+        day_phrase: The day's phrase
+        pin: Optional static PIN
+        rsa_key_data: Optional RSA key bytes
+        
+    Returns:
+        Decrypted message string
+        
+    Raises:
+        DecryptionError: If decryption fails or content is a file
+    """
+    result = decrypt_message(encrypted_data, photo_data, day_phrase, pin, rsa_key_data)
+    
+    if result.is_file:
+        if result.file_data:
+            # Try to decode as text
+            try:
+                return result.file_data.decode('utf-8')
+            except UnicodeDecodeError:
+                raise DecryptionError(
+                    f"Content is a binary file ({result.filename or 'unnamed'}), not text"
+                )
+        return ""
+    
+    return result.message or ""
+
+
 def get_date_from_encrypted(encrypted_data: bytes) -> Optional[str]:
     """
     Extract the date string from encrypted data without decrypting.
diff --git a/src/stegasoo/models.py b/src/stegasoo/models.py
index 6a9109a..747de21 100644
--- a/src/stegasoo/models.py
+++ b/src/stegasoo/models.py
@@ -6,7 +6,7 @@ Dataclasses for structured data exchange between modules and frontends.
 
 from dataclasses import dataclass, field
 from datetime import date
-from typing import Optional
+from typing import Optional, Union
 
 
 @dataclass
@@ -43,10 +43,35 @@ class Credentials:
         return self.phrase_entropy + self.pin_entropy + self.rsa_entropy
 
 
+@dataclass
+class FilePayload:
+    """Represents a file to be embedded."""
+    data: bytes
+    filename: str
+    mime_type: Optional[str] = None
+    
+    @property
+    def size(self) -> int:
+        return len(self.data)
+    
+    @classmethod
+    def from_file(cls, filepath: str, filename: Optional[str] = None) -> 'FilePayload':
+        """Create FilePayload from a file path."""
+        from pathlib import Path
+        import mimetypes
+        
+        path = Path(filepath)
+        data = path.read_bytes()
+        name = filename or path.name
+        mime, _ = mimetypes.guess_type(name)
+        
+        return cls(data=data, filename=name, mime_type=mime)
+
+
 @dataclass
 class EncodeInput:
     """Input parameters for encoding a message."""
-    message: str
+    message: Union[str, bytes, FilePayload]  # Text, raw bytes, or file
     reference_photo: bytes
     carrier_image: bytes
     day_phrase: str
@@ -90,8 +115,26 @@ class DecodeInput:
 @dataclass
 class DecodeResult:
     """Result of decoding operation."""
-    message: str
-    date_encoded: str
+    payload_type: str  # 'text' or 'file'
+    message: Optional[str] = None  # For text payloads
+    file_data: Optional[bytes] = None  # For file payloads
+    filename: Optional[str] = None  # Original filename for file payloads
+    mime_type: Optional[str] = None  # MIME type hint
+    date_encoded: Optional[str] = None
+    
+    @property
+    def is_file(self) -> bool:
+        return self.payload_type == 'file'
+    
+    @property
+    def is_text(self) -> bool:
+        return self.payload_type == 'text'
+    
+    def get_content(self) -> Union[str, bytes]:
+        """Get the decoded content (text or bytes)."""
+        if self.is_text:
+            return self.message or ""
+        return self.file_data or b""
 
 
 @dataclass 
diff --git a/src/stegasoo/steganography.py b/src/stegasoo/steganography.py
index 510c8a4..d9f5f12 100644
--- a/src/stegasoo/steganography.py
+++ b/src/stegasoo/steganography.py
@@ -16,6 +16,43 @@ from .models import EmbedStats
 from .exceptions import CapacityError, ExtractionError, EmbeddingError
 
 
+# Lossless formats that preserve LSB data
+LOSSLESS_FORMATS = {'PNG', 'BMP', 'TIFF'}
+
+# Format to extension mapping
+FORMAT_TO_EXT = {
+    'PNG': 'png',
+    'BMP': 'bmp',
+    'TIFF': 'tiff',
+}
+
+# Extension to PIL format mapping
+EXT_TO_FORMAT = {
+    'png': 'PNG',
+    'bmp': 'BMP',
+    'tiff': 'TIFF',
+    'tif': 'TIFF',
+}
+
+
+def get_output_format(input_format: Optional[str]) -> tuple[str, str]:
+    """
+    Determine the output format based on input format.
+    
+    Args:
+        input_format: PIL format string of input image (e.g., 'JPEG', 'PNG')
+        
+    Returns:
+        Tuple of (PIL format string, file extension) for output
+        Falls back to PNG for lossy or unknown formats.
+    """
+    if input_format and input_format.upper() in LOSSLESS_FORMATS:
+        fmt = input_format.upper()
+        return fmt, FORMAT_TO_EXT.get(fmt, 'png')
+    # Default to PNG for lossy formats (JPEG, GIF) or unknown
+    return 'PNG', 'png'
+
+
 def generate_pixel_indices(key: bytes, num_pixels: int, num_needed: int) -> list[int]:
     """
     Generate pseudo-random pixel indices for embedding.
@@ -83,8 +120,9 @@ def embed_in_image(
     carrier_data: bytes,
     encrypted_data: bytes,
     pixel_key: bytes,
-    bits_per_channel: int = 1
-) -> tuple[bytes, EmbedStats]:
+    bits_per_channel: int = 1,
+    output_format: Optional[str] = None
+) -> tuple[bytes, EmbedStats, str]:
     """
     Embed encrypted data in carrier image using LSB steganography.
     
@@ -96,9 +134,11 @@ def embed_in_image(
         encrypted_data: Data to embed
         pixel_key: Key for pixel selection
         bits_per_channel: Bits to use per color channel (1-2)
+        output_format: Force specific output format (PNG, BMP). 
+                       If None, auto-detect from carrier (lossless) or default to PNG.
         
     Returns:
-        Tuple of (PNG image bytes, EmbedStats)
+        Tuple of (image bytes, EmbedStats, file extension)
         
     Raises:
         CapacityError: If carrier is too small
@@ -106,6 +146,8 @@ def embed_in_image(
     """
     try:
         img = Image.open(io.BytesIO(carrier_data))
+        input_format = img.format
+        
         if img.mode != 'RGB':
             img = img.convert('RGB')
         
@@ -160,8 +202,15 @@ def embed_in_image(
         stego_img = Image.new('RGB', img.size)
         stego_img.putdata(new_pixels)
         
+        # Determine output format
+        if output_format:
+            out_fmt = output_format.upper()
+            out_ext = FORMAT_TO_EXT.get(out_fmt, 'png')
+        else:
+            out_fmt, out_ext = get_output_format(input_format)
+        
         output = io.BytesIO()
-        stego_img.save(output, 'PNG')
+        stego_img.save(output, out_fmt)
         output.seek(0)
         
         stats = EmbedStats(
@@ -171,7 +220,7 @@ def embed_in_image(
             bytes_embedded=len(data_with_len)
         )
         
-        return output.getvalue(), stats
+        return output.getvalue(), stats, out_ext
         
     except CapacityError:
         raise
@@ -284,3 +333,18 @@ def get_image_dimensions(image_data: bytes) -> tuple[int, int]:
     """Get image dimensions without loading full image."""
     img = Image.open(io.BytesIO(image_data))
     return img.size
+
+
+def get_image_format(image_data: bytes) -> Optional[str]:
+    """Get image format (PIL format string like 'PNG', 'JPEG')."""
+    try:
+        img = Image.open(io.BytesIO(image_data))
+        return img.format
+    except Exception:
+        return None
+
+
+def is_lossless_format(image_data: bytes) -> bool:
+    """Check if image is in a lossless format suitable for steganography."""
+    fmt = get_image_format(image_data)
+    return fmt is not None and fmt.upper() in LOSSLESS_FORMATS
diff --git a/src/stegasoo/utils.py b/src/stegasoo/utils.py
index cafbf54..9c4c7a2 100644
--- a/src/stegasoo/utils.py
+++ b/src/stegasoo/utils.py
@@ -15,15 +15,20 @@ from typing import Optional
 from .constants import DAY_NAMES
 
 
-def generate_filename(date_str: Optional[str] = None, prefix: str = "") -> str:
+def generate_filename(
+    date_str: Optional[str] = None,
+    prefix: str = "",
+    extension: str = "png"
+) -> str:
     """
     Generate a filename for stego images.
     
-    Format: {prefix}{random}_{YYYYMMDD}.png
+    Format: {prefix}{random}_{YYYYMMDD}.{extension}
     
     Args:
         date_str: Date string (YYYY-MM-DD), defaults to today
         prefix: Optional prefix
+        extension: File extension without dot (default: 'png')
         
     Returns:
         Filename string
@@ -34,7 +39,10 @@ def generate_filename(date_str: Optional[str] = None, prefix: str = "") -> str:
     date_compact = date_str.replace('-', '')
     random_hex = secrets.token_hex(4)
     
-    return f"{prefix}{random_hex}_{date_compact}.png"
+    # Ensure extension doesn't have a leading dot
+    extension = extension.lstrip('.')
+    
+    return f"{prefix}{random_hex}_{date_compact}.{extension}"
 
 
 def parse_date_from_filename(filename: str) -> Optional[str]:
diff --git a/src/stegasoo/validation.py b/src/stegasoo/validation.py
index da338aa..9917d77 100644
--- a/src/stegasoo/validation.py
+++ b/src/stegasoo/validation.py
@@ -5,17 +5,17 @@ Validators for all user inputs with clear error messages.
 """
 
 import io
-from typing import Optional
+from typing import Optional, Union
 
 from PIL import Image
 
 from .constants import (
     MIN_PIN_LENGTH, MAX_PIN_LENGTH,
-    MAX_MESSAGE_SIZE, MAX_IMAGE_PIXELS, MAX_FILE_SIZE,
+    MAX_MESSAGE_SIZE, MAX_FILE_PAYLOAD_SIZE, MAX_IMAGE_PIXELS, MAX_FILE_SIZE,
     MIN_RSA_BITS, MIN_KEY_PASSWORD_LENGTH,
     ALLOWED_IMAGE_EXTENSIONS, ALLOWED_KEY_EXTENSIONS,
 )
-from .models import ValidationResult
+from .models import ValidationResult, FilePayload
 from .exceptions import (
     ValidationError, PinValidationError, MessageValidationError,
     ImageValidationError, KeyValidationError, SecurityFactorError,
@@ -61,7 +61,7 @@ def validate_pin(pin: str, required: bool = False) -> ValidationResult:
 
 def validate_message(message: str) -> ValidationResult:
     """
-    Validate message content and size.
+    Validate text message content and size.
     
     Args:
         message: Message text
@@ -80,6 +80,81 @@ def validate_message(message: str) -> ValidationResult:
     return ValidationResult.ok(length=len(message))
 
 
+def validate_payload(payload: Union[str, bytes, FilePayload]) -> ValidationResult:
+    """
+    Validate a payload (text message, bytes, or file).
+    
+    Args:
+        payload: Text string, raw bytes, or FilePayload
+        
+    Returns:
+        ValidationResult
+    """
+    if isinstance(payload, str):
+        return validate_message(payload)
+    
+    elif isinstance(payload, FilePayload):
+        if not payload.data:
+            return ValidationResult.error("File is empty")
+        
+        if len(payload.data) > MAX_FILE_PAYLOAD_SIZE:
+            return ValidationResult.error(
+                f"File too large ({len(payload.data):,} bytes). "
+                f"Maximum: {MAX_FILE_PAYLOAD_SIZE:,} bytes ({MAX_FILE_PAYLOAD_SIZE // 1024} KB)"
+            )
+        
+        return ValidationResult.ok(
+            size=len(payload.data),
+            filename=payload.filename,
+            mime_type=payload.mime_type
+        )
+    
+    elif isinstance(payload, bytes):
+        if not payload:
+            return ValidationResult.error("Payload is empty")
+        
+        if len(payload) > MAX_FILE_PAYLOAD_SIZE:
+            return ValidationResult.error(
+                f"Payload too large ({len(payload):,} bytes). "
+                f"Maximum: {MAX_FILE_PAYLOAD_SIZE:,} bytes ({MAX_FILE_PAYLOAD_SIZE // 1024} KB)"
+            )
+        
+        return ValidationResult.ok(size=len(payload))
+    
+    else:
+        return ValidationResult.error(f"Invalid payload type: {type(payload)}")
+
+
+def validate_file_payload(
+    file_data: bytes,
+    filename: str = "",
+    max_size: int = MAX_FILE_PAYLOAD_SIZE
+) -> ValidationResult:
+    """
+    Validate a file for embedding.
+    
+    Args:
+        file_data: Raw file bytes
+        filename: Original filename (for display in errors)
+        max_size: Maximum allowed size in bytes
+        
+    Returns:
+        ValidationResult
+    """
+    if not file_data:
+        return ValidationResult.error("File is empty")
+    
+    if len(file_data) > max_size:
+        size_kb = len(file_data) / 1024
+        max_kb = max_size / 1024
+        return ValidationResult.error(
+            f"File '{filename or 'unnamed'}' too large ({size_kb:.1f} KB). "
+            f"Maximum: {max_kb:.0f} KB"
+        )
+    
+    return ValidationResult.ok(size=len(file_data), filename=filename)
+
+
 def validate_image(
     image_data: bytes,
     name: str = "Image",
@@ -319,6 +394,13 @@ def require_valid_message(message: str) -> None:
         raise MessageValidationError(result.error_message)
 
 
+def require_valid_payload(payload: Union[str, bytes, FilePayload]) -> None:
+    """Validate payload (text, bytes, or file), raising exception on failure."""
+    result = validate_payload(payload)
+    if not result.is_valid:
+        raise MessageValidationError(result.error_message)
+
+
 def require_valid_image(image_data: bytes, name: str = "Image") -> None:
     """Validate image, raising exception on failure."""
     result = validate_image(image_data, name)
diff --git a/test_data/holmes_shit_20251228.png b/test_data/holmes_shit_20251228.png
new file mode 100644
index 0000000..f123724
Binary files /dev/null and b/test_data/holmes_shit_20251228.png differ
diff --git a/test_data/scandal.txt.gz b/test_data/scandal.txt.gz
new file mode 100644
index 0000000..bc9d70a
Binary files /dev/null and b/test_data/scandal.txt.gz differ
diff --git a/test_data/scandal.txt.gz.b64 b/test_data/scandal.txt.gz.b64
new file mode 100644
index 0000000..5b9922b
--- /dev/null
+++ b/test_data/scandal.txt.gz.b64
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+D189PWmLfvfxh+/1dzWF8mJ6CU7dPJ//+i//Mvk+xWSo7vTY+D0QecUBGAWe8nfSoAr9eopNkMFK
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diff --git a/tests/test_stegasoo.py b/tests/test_stegasoo.py
index 7c9217a..05a7ce7 100644
--- a/tests/test_stegasoo.py
+++ b/tests/test_stegasoo.py
@@ -22,6 +22,7 @@ from stegasoo import (
     decode,
     DAY_NAMES,
 )
+from stegasoo.steganography import get_output_format, get_image_format
 
 
 class TestKeygen:
@@ -127,19 +128,71 @@ class TestValidation:
         assert not result.is_valid
 
 
+class TestOutputFormat:
+    """Test output format detection and preservation."""
+    
+    def test_png_stays_png(self):
+        fmt, ext = get_output_format('PNG')
+        assert fmt == 'PNG'
+        assert ext == 'png'
+    
+    def test_bmp_stays_bmp(self):
+        fmt, ext = get_output_format('BMP')
+        assert fmt == 'BMP'
+        assert ext == 'bmp'
+    
+    def test_jpeg_becomes_png(self):
+        fmt, ext = get_output_format('JPEG')
+        assert fmt == 'PNG'
+        assert ext == 'png'
+    
+    def test_gif_becomes_png(self):
+        fmt, ext = get_output_format('GIF')
+        assert fmt == 'PNG'
+        assert ext == 'png'
+    
+    def test_none_becomes_png(self):
+        fmt, ext = get_output_format(None)
+        assert fmt == 'PNG'
+        assert ext == 'png'
+    
+    def test_unknown_becomes_png(self):
+        fmt, ext = get_output_format('WEBP')
+        assert fmt == 'PNG'
+        assert ext == 'png'
+
+
 class TestEncodeDecode:
     """Test encoding and decoding (requires test images)."""
     
     @pytest.fixture
-    def test_image(self):
-        """Create a simple test image."""
+    def png_image(self):
+        """Create a simple PNG test image."""
         from PIL import Image
         img = Image.new('RGB', (100, 100), color='red')
         buf = io.BytesIO()
         img.save(buf, format='PNG')
         return buf.getvalue()
     
-    def test_encode_decode_roundtrip(self, test_image):
+    @pytest.fixture
+    def bmp_image(self):
+        """Create a simple BMP test image."""
+        from PIL import Image
+        img = Image.new('RGB', (100, 100), color='blue')
+        buf = io.BytesIO()
+        img.save(buf, format='BMP')
+        return buf.getvalue()
+    
+    @pytest.fixture
+    def jpeg_image(self):
+        """Create a simple JPEG test image."""
+        from PIL import Image
+        img = Image.new('RGB', (100, 100), color='green')
+        buf = io.BytesIO()
+        img.save(buf, format='JPEG', quality=95)
+        return buf.getvalue()
+    
+    def test_encode_decode_roundtrip(self, png_image):
         """Test full encode/decode cycle."""
         message = "Secret message!"
         phrase = "apple forest thunder"
@@ -147,8 +200,8 @@ class TestEncodeDecode:
         
         result = encode(
             message=message,
-            reference_photo=test_image,
-            carrier_image=test_image,
+            reference_photo=png_image,
+            carrier_image=png_image,
             day_phrase=phrase,
             pin=pin
         )
@@ -159,19 +212,89 @@ class TestEncodeDecode:
         
         decoded = decode(
             stego_image=result.stego_image,
-            reference_photo=test_image,
+            reference_photo=png_image,
             day_phrase=phrase,
             pin=pin
         )
         
         assert decoded == message
     
-    def test_wrong_pin_fails(self, test_image):
+    def test_png_carrier_produces_png(self, png_image):
+        """Test that PNG carrier produces PNG output."""
+        result = encode(
+            message="Test",
+            reference_photo=png_image,
+            carrier_image=png_image,
+            day_phrase="test phrase here",
+            pin="123456"
+        )
+        
+        assert result.filename.endswith('.png')
+        # Verify actual format
+        output_format = get_image_format(result.stego_image)
+        assert output_format == 'PNG'
+    
+    def test_bmp_carrier_produces_bmp(self, bmp_image, png_image):
+        """Test that BMP carrier produces BMP output."""
+        result = encode(
+            message="Test",
+            reference_photo=png_image,
+            carrier_image=bmp_image,
+            day_phrase="test phrase here",
+            pin="123456"
+        )
+        
+        assert result.filename.endswith('.bmp')
+        # Verify actual format
+        output_format = get_image_format(result.stego_image)
+        assert output_format == 'BMP'
+    
+    def test_jpeg_carrier_produces_png(self, jpeg_image, png_image):
+        """Test that JPEG carrier produces PNG output (lossy -> lossless)."""
+        result = encode(
+            message="Test",
+            reference_photo=png_image,
+            carrier_image=jpeg_image,
+            day_phrase="test phrase here",
+            pin="123456"
+        )
+        
+        assert result.filename.endswith('.png')
+        # Verify actual format
+        output_format = get_image_format(result.stego_image)
+        assert output_format == 'PNG'
+    
+    def test_bmp_roundtrip(self, bmp_image, png_image):
+        """Test full encode/decode cycle with BMP."""
+        message = "BMP test message!"
+        phrase = "test phrase words"
+        pin = "123456"
+        
+        result = encode(
+            message=message,
+            reference_photo=png_image,
+            carrier_image=bmp_image,
+            day_phrase=phrase,
+            pin=pin
+        )
+        
+        assert result.filename.endswith('.bmp')
+        
+        decoded = decode(
+            stego_image=result.stego_image,
+            reference_photo=png_image,
+            day_phrase=phrase,
+            pin=pin
+        )
+        
+        assert decoded == message
+    
+    def test_wrong_pin_fails(self, png_image):
         """Test that wrong PIN fails to decode."""
         result = encode(
             message="Secret",
-            reference_photo=test_image,
-            carrier_image=test_image,
+            reference_photo=png_image,
+            carrier_image=png_image,
             day_phrase="test phrase here",
             pin="123456"
         )
@@ -179,17 +302,17 @@ class TestEncodeDecode:
         with pytest.raises(stegasoo.DecryptionError):
             decode(
                 stego_image=result.stego_image,
-                reference_photo=test_image,
+                reference_photo=png_image,
                 day_phrase="test phrase here",
                 pin="654321"  # Wrong PIN
             )
     
-    def test_wrong_phrase_fails(self, test_image):
+    def test_wrong_phrase_fails(self, png_image):
         """Test that wrong phrase fails to decode."""
         result = encode(
             message="Secret",
-            reference_photo=test_image,
-            carrier_image=test_image,
+            reference_photo=png_image,
+            carrier_image=png_image,
             day_phrase="correct phrase here",
             pin="123456"
         )
@@ -197,7 +320,7 @@ class TestEncodeDecode:
         with pytest.raises(stegasoo.DecryptionError):
             decode(
                 stego_image=result.stego_image,
-                reference_photo=test_image,
+                reference_photo=png_image,
                 day_phrase="wrong phrase here",
                 pin="123456"
             )