Invisible watermarks
An invisible watermark hides an ID in the content itself, so it stays when the metadata goes: through re-encoding, resizing and re-uploads. Kennmarq.com uses three open-source models, one for each kind of file, and reads every mark back before the file leaves.
In short
- Images: TrustMark, by Adobe.
- Video: Video Seal, by Meta, in every frame.
- Audio: AudioSeal, by Meta, under the music.
- Why: it leads back to the file's Content Credentials when platforms strip them, as the EU's Code of Practice asks.
What each one carries
| File | Watermark | Carries | Checked |
|---|---|---|---|
| Images | TrustMark (variant Q), open source, by Adobe; on the C2PA's list of soft bindings | A random 61-bit ID that leads to the image's credential | All 78 test images after JPEG at quality 50, a social-network-style resize and a resize to 25% (report) |
| Video | Video Seal, open source, by Meta | The same kind of 61-bit ID, in every frame | Read back from 64 frames of every clip before it leaves |
| Audio | AudioSeal, open source, by Meta | 16 bits that say the sound was marked by us; the song's credential travels in its manifest | Read back from the encoded file; shaped under the music, so no one hears it |
What an image's watermark survives
From our robustness report, measured on 78 AI images with the code the API runs: the ID read back after JPEG at quality 50 in 100% of them, after a social network's kind of upload (long side 1080 px, JPEG 85) in 100%, after a resize to 25% in 100%, after a 2-pixel blur in 100%, and after a crop to the centre 90% in 100%. Harder edits cost more: a crop to the centre 75% kept 53%, and a 5° rotation 41%. The report has every edit, with error bars, and how often unmarked images read as marked.
Reading them
- Images: kennmarq.com/check, free, in the browser; it also reads quarter-turned images.
- Images, video and audio: POST /v1/verify (video and audio with a key).
What a watermark is not
A watermark says a file was marked; it isn't an AI detector, and its absence doesn't prove a file is human-made. Very quiet recordings may not hold an audio mark: their credential then says so.