diff --git a/.gitignore b/.gitignore
index bb5d1d5..4b7914f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -68,6 +68,7 @@ test_data/*.png
 scripts/*
 !scripts/validate-release.sh
 !scripts/smoke-test.sh
+!scripts/setup-trusted-certs.sh
 
 # Web UI auth database and SSL certs
 instance/
diff --git a/frontends/web/docker-entrypoint.sh b/frontends/web/docker-entrypoint.sh
index 460109a..99d4f6f 100644
--- a/frontends/web/docker-entrypoint.sh
+++ b/frontends/web/docker-entrypoint.sh
@@ -3,6 +3,8 @@
 # Docker entrypoint for Stegasoo Web UI
 # Handles SSL certificate generation and gunicorn startup
 #
+# Supports mkcert for browser-trusted certificates (no warning screen)
+#
 
 set -e
 
@@ -11,24 +13,42 @@ CERT_FILE="$CERT_DIR/cert.pem"
 KEY_FILE="$CERT_DIR/key.pem"
 HOSTNAME="${STEGASOO_HOSTNAME:-localhost}"
 
-# Generate self-signed SSL certificate if HTTPS enabled and certs don't exist
+# Generate SSL certificates
+# Priority: 1) Existing certs, 2) mkcert (trusted), 3) openssl (self-signed)
 generate_certs() {
-    if [ ! -f "$CERT_FILE" ] || [ ! -f "$KEY_FILE" ]; then
-        echo "Generating self-signed SSL certificate for $HOSTNAME..."
-        mkdir -p "$CERT_DIR"
-
-        openssl req -x509 -newkey rsa:2048 \
-            -keyout "$KEY_FILE" \
-            -out "$CERT_FILE" \
-            -sha256 -days 365 -nodes \
-            -subj "/CN=$HOSTNAME" \
-            -addext "subjectAltName=DNS:$HOSTNAME,DNS:localhost,IP:127.0.0.1" \
-            2>/dev/null
-
-        echo "SSL certificate generated."
-    else
+    if [ -f "$CERT_FILE" ] && [ -f "$KEY_FILE" ]; then
         echo "Using existing SSL certificates."
+        return
     fi
+
+    mkdir -p "$CERT_DIR"
+
+    # Try mkcert first (creates browser-trusted certs)
+    if command -v mkcert &> /dev/null; then
+        echo "Generating trusted certificate with mkcert for $HOSTNAME..."
+        cd "$CERT_DIR"
+        mkcert -key-file key.pem -cert-file cert.pem "$HOSTNAME" localhost 127.0.0.1 ::1
+        echo "Trusted certificate generated."
+        echo ""
+        echo "  To trust on other devices, install the CA cert from:"
+        echo "  $(mkcert -CAROOT)/rootCA.pem"
+        echo ""
+        return
+    fi
+
+    # Fallback to self-signed (shows browser warning)
+    echo "Generating self-signed SSL certificate for $HOSTNAME..."
+    echo "(Install mkcert for browser-trusted certs without warnings)"
+
+    openssl req -x509 -newkey rsa:2048 \
+        -keyout "$KEY_FILE" \
+        -out "$CERT_FILE" \
+        -sha256 -days 365 -nodes \
+        -subj "/CN=$HOSTNAME" \
+        -addext "subjectAltName=DNS:$HOSTNAME,DNS:localhost,IP:127.0.0.1" \
+        2>/dev/null
+
+    echo "Self-signed certificate generated."
 }
 
 # Start gunicorn with appropriate settings
diff --git a/rpi/setup.sh b/rpi/setup.sh
index 70291f5..ca947c2 100755
--- a/rpi/setup.sh
+++ b/rpi/setup.sh
@@ -184,6 +184,20 @@ else
     echo "  gum already installed"
 fi
 
+# Install mkcert for browser-trusted certificates (no warning screen!)
+echo "  Installing mkcert for trusted HTTPS certificates..."
+if ! command -v mkcert &>/dev/null; then
+    sudo apt-get install -y libnss3-tools
+    # Download mkcert for ARM64
+    sudo curl -sL "https://github.com/FiloSottile/mkcert/releases/download/v1.4.4/mkcert-v1.4.4-linux-arm64" -o /usr/local/bin/mkcert
+    sudo chmod +x /usr/local/bin/mkcert
+    # Install local CA (makes certs trusted on this Pi)
+    mkcert -install 2>/dev/null || true
+    echo "  mkcert installed"
+else
+    echo "  mkcert already installed"
+fi
+
 echo -e "${GREEN}[4/12]${NC} Cloning Stegasoo..."
 
 # Clone Stegasoo first (needed to check for pre-built tarball)
@@ -593,19 +607,40 @@ if [ "$ENABLE_HTTPS" = "true" ]; then
     LOCAL_IP=$(hostname -I | awk '{print $1}')
     PI_HOSTNAME=$(hostname)
 
-    # Generate cert with SANs for IP, hostname, and localhost
-    openssl req -x509 -newkey rsa:2048 \
-      -keyout "$CERT_DIR/server.key" \
-      -out "$CERT_DIR/server.crt" \
-      -days 365 -nodes \
-      -subj "/O=Stegasoo/CN=$PI_HOSTNAME" \
-      -addext "subjectAltName=DNS:$PI_HOSTNAME,DNS:$PI_HOSTNAME.local,DNS:localhost,IP:$LOCAL_IP,IP:127.0.0.1" \
-      2>/dev/null
+    # Try mkcert first (creates browser-trusted certs - no warning screen!)
+    if command -v mkcert &> /dev/null; then
+        echo "  Using mkcert for browser-trusted certificates..."
+        cd "$CERT_DIR"
+        mkcert -key-file server.key -cert-file server.crt \
+            "$PI_HOSTNAME" "$PI_HOSTNAME.local" localhost "$LOCAL_IP" 127.0.0.1 ::1
+
+        # Copy CA to web-accessible location for easy device setup
+        CA_ROOT=$(mkcert -CAROOT)
+        CA_DIR="$INSTALL_DIR/frontends/web/static/ca"
+        mkdir -p "$CA_DIR"
+        cp "$CA_ROOT/rootCA.pem" "$CA_DIR/"
+
+        echo -e "  ${GREEN}✓${NC} Trusted certificates generated with mkcert"
+        echo -e "  ${CYAN}Tip:${NC} New devices can get the CA from: http://$PI_HOSTNAME.local/static/ca/rootCA.pem"
+    else
+        # Fallback to self-signed (shows browser warning)
+        echo "  Using self-signed certificate (browser will show warning)"
+        echo "  Tip: Install mkcert for trusted certs without warnings"
+
+        openssl req -x509 -newkey rsa:2048 \
+          -keyout "$CERT_DIR/server.key" \
+          -out "$CERT_DIR/server.crt" \
+          -days 365 -nodes \
+          -subj "/O=Stegasoo/CN=$PI_HOSTNAME" \
+          -addext "subjectAltName=DNS:$PI_HOSTNAME,DNS:$PI_HOSTNAME.local,DNS:localhost,IP:$LOCAL_IP,IP:127.0.0.1" \
+          2>/dev/null
+
+        echo -e "  ${GREEN}✓${NC} Self-signed certificates generated"
+    fi
 
     # Fix permissions
     chmod 600 "$CERT_DIR/server.key"
     chown -R "$USER:$USER" "$CERT_DIR"
-    echo -e "  ${GREEN}✓${NC} SSL certificates generated"
 fi
 
 # Setup port 443 redirect if requested
diff --git a/scripts/setup-trusted-certs.sh b/scripts/setup-trusted-certs.sh
new file mode 100755
index 0000000..9946afc
--- /dev/null
+++ b/scripts/setup-trusted-certs.sh
@@ -0,0 +1,149 @@
+#!/bin/bash
+#
+# Setup trusted HTTPS certificates for Stegasoo
+# Uses mkcert to create browser-trusted certs (no warning screens!)
+#
+# Usage: ./setup-trusted-certs.sh [hostname]
+#
+# This script:
+#   1. Installs mkcert if needed
+#   2. Creates a local CA (one-time)
+#   3. Generates certs for your hostname
+#   4. Shows how to trust the CA on other devices
+#
+
+set -e
+
+HOSTNAME="${1:-stegasoo.local}"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$SCRIPT_DIR/.."
+CERT_DIR="$PROJECT_ROOT/frontends/web/certs"
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+CYAN='\033[0;36m'
+NC='\033[0m'
+
+echo ""
+echo -e "${CYAN}╔═══════════════════════════════════════════════════════════════╗${NC}"
+echo -e "${CYAN}║         Stegasoo Trusted Certificate Setup                    ║${NC}"
+echo -e "${CYAN}╚═══════════════════════════════════════════════════════════════╝${NC}"
+echo ""
+
+# Check/install mkcert
+install_mkcert() {
+    if command -v mkcert &> /dev/null; then
+        echo -e "${GREEN}✓${NC} mkcert already installed"
+        return
+    fi
+
+    echo -e "${YELLOW}Installing mkcert...${NC}"
+
+    # Detect OS and install
+    if [[ "$OSTYPE" == "darwin"* ]]; then
+        # macOS
+        if command -v brew &> /dev/null; then
+            brew install mkcert
+        else
+            echo -e "${RED}Please install Homebrew first: https://brew.sh${NC}"
+            exit 1
+        fi
+    elif [[ -f /etc/debian_version ]]; then
+        # Debian/Ubuntu/Raspberry Pi OS
+        sudo apt-get update
+        sudo apt-get install -y libnss3-tools
+
+        # Download mkcert binary
+        ARCH=$(dpkg --print-architecture)
+        if [[ "$ARCH" == "arm64" ]] || [[ "$ARCH" == "aarch64" ]]; then
+            MKCERT_URL="https://github.com/FiloSottile/mkcert/releases/latest/download/mkcert-linux-arm64"
+        else
+            MKCERT_URL="https://github.com/FiloSottile/mkcert/releases/latest/download/mkcert-linux-amd64"
+        fi
+
+        sudo curl -L "$MKCERT_URL" -o /usr/local/bin/mkcert
+        sudo chmod +x /usr/local/bin/mkcert
+    elif [[ -f /etc/arch-release ]]; then
+        # Arch Linux
+        sudo pacman -S mkcert
+    else
+        echo -e "${RED}Unsupported OS. Please install mkcert manually:${NC}"
+        echo "  https://github.com/FiloSottile/mkcert#installation"
+        exit 1
+    fi
+
+    echo -e "${GREEN}✓${NC} mkcert installed"
+}
+
+# Install local CA
+setup_ca() {
+    echo ""
+    echo -e "${CYAN}Setting up local Certificate Authority...${NC}"
+
+    if mkcert -install 2>/dev/null; then
+        echo -e "${GREEN}✓${NC} Local CA installed in system trust store"
+    else
+        echo -e "${YELLOW}!${NC} Could not auto-install CA (may need manual browser import)"
+    fi
+}
+
+# Generate certificates
+generate_certs() {
+    echo ""
+    echo -e "${CYAN}Generating trusted certificate for: ${YELLOW}$HOSTNAME${NC}"
+
+    mkdir -p "$CERT_DIR"
+    cd "$CERT_DIR"
+
+    # Generate cert for hostname + common local names
+    mkcert -key-file key.pem -cert-file cert.pem \
+        "$HOSTNAME" \
+        localhost \
+        127.0.0.1 \
+        ::1
+
+    echo -e "${GREEN}✓${NC} Certificates generated in: $CERT_DIR"
+}
+
+# Show CA location for other devices
+show_ca_info() {
+    CA_ROOT=$(mkcert -CAROOT)
+    CA_FILE="$CA_ROOT/rootCA.pem"
+
+    echo ""
+    echo -e "${CYAN}════════════════════════════════════════════════════════════════${NC}"
+    echo -e "${GREEN}  Setup Complete!${NC}"
+    echo -e "${CYAN}════════════════════════════════════════════════════════════════${NC}"
+    echo ""
+    echo "Your certificates are ready. Browsers on THIS machine will trust them."
+    echo ""
+    echo -e "${YELLOW}To trust on OTHER devices (phones, tablets, other computers):${NC}"
+    echo ""
+    echo "  1. Copy the CA certificate to that device:"
+    echo -e "     ${CYAN}$CA_FILE${NC}"
+    echo ""
+    echo "  2. Import it as a trusted CA:"
+    echo "     - iOS: AirDrop/email the file, Settings > Profile Downloaded > Install"
+    echo "     - Android: Settings > Security > Install from storage"
+    echo "     - Windows: Double-click > Install > Trusted Root CAs"
+    echo "     - macOS: Double-click > Keychain Access > Trust Always"
+    echo "     - Linux: Copy to /usr/local/share/ca-certificates/ && update-ca-certificates"
+    echo ""
+    echo -e "${YELLOW}Quick copy command:${NC}"
+    echo "  scp $CA_FILE user@device:/path/"
+    echo ""
+
+    # Offer to serve CA file via HTTP for easy phone download
+    echo -e "${YELLOW}Or serve the CA for easy phone download:${NC}"
+    echo "  python3 -m http.server 8080 -d $CA_ROOT"
+    echo "  Then visit: http://$(hostname -I | awk '{print $1}'):8080/rootCA.pem"
+    echo ""
+}
+
+# Main
+install_mkcert
+setup_ca
+generate_certs
+show_ca_info