FaintMark MCP server

FaintMark

Invisible per-recipient image watermarks. Create one marked copy per recipient, then identify which copy a shared or leaked image is. Designed to tolerate the recompression and resizing chat apps apply; see the app tests and limits below. Runs locally, no account, no upload. Python CLI and MCP server.

$ faintmark mark photo.jpg alice bob
alice  991e318a21  /Users/me/Pictures/marked/photo-991e318a21.jpg
bob  746ac9fa88  /Users/me/Pictures/marked/photo-746ac9fa88.jpg
2 copies in /Users/me/Pictures/marked

$ faintmark check ~/Downloads/forwarded.jpg
matched: alice  991e318a21  marked 2026-10-06T23:11:54Z

Send each person only their own file; file names carry the id, not the name. A match identifies the label the copy was issued under, not who shared it. The mark is intended to be visually unobtrusive on photographs. JPEG, PNG and WebP keep their format; HEIC becomes JPEG.

Install

uvx faintmark mark photo.jpg alice bob   # runs without installing; needs uv
uv tool install faintmark                # or: pipx install faintmark

Python 3.11 or newer on macOS, Linux or Windows (Intel Macs: 3.11 to 3.13). uv can install Python and run FaintMark. The first mark or check downloads Adobe's TrustMark Q models (65 MB, SHA-256 verified) into ~/.faintmark. For HEIC input install faintmark[heic]: uv tool install 'faintmark[heic]', or without a persistent install uvx --from 'faintmark[heic]' faintmark mark photo.heic alice. uv tool uninstall faintmark removes the command and leaves ~/.faintmark in place.

faintmark mark IMAGE RECIPIENT... [-o DIR] [--format png|jpeg|webp] [--json]
faintmark check IMAGE [--deep] [--files] [--json]
faintmark list [-n N] [--files] [--json]

Copies go into marked/ beside the image unless -o says otherwise. Quote labels with spaces: faintmark mark photo.jpg 'Alice Smith'. One run marks 1 to 100 recipients. --json prints the result the matching MCP tool returns; mark includes the source file name and output paths, check and list omit file names and paths unless --files is set. check --deep also tries a flip and small rotations, and when nothing is detected lists up to three registered ids within 26 of 96 codeword bits of the raw decoder output as candidates, with their bit distance. Those are uncalibrated and can be coincidental or forged; they are never a match. With --json, errors print {"error": "..."}. check exits 0 for matched, 1 for unregistered or not_detected, 2 for an error.

mark accepts non-animated JPEG, PNG, WebP and HEIC up to 25 megapixels without transparency (16-bit RGB is read at 8 bits; 16-bit grayscale and CMYK are rejected) and needs about 1.5 GB of memory at that size. check reads the first frame of anything Pillow opens, up to 100 megapixels.

Agents

claude mcp add --scope user faintmark -- uvx faintmark mcp
codex mcp add faintmark -- uvx faintmark mcp
gemini mcp add -s user faintmark uvx faintmark mcp

Any other client that reads an mcpServers config (Claude Desktop, Cursor, Windsurf): add this entry to the client's MCP configuration. The client must find uvx on its PATH; set FAINTMARK_HOME in the server's environment to use another registry.

{ "mcpServers": { "faintmark": { "type": "stdio", "command": "uvx", "args": ["faintmark", "mcp"] } } }

Shortened. The full README is on GitHub.