If you assume competence from Google, they probably have two different watermarks. A sloppy one they offer an online oracle for and one they keep in reserve for themselves (and law enforcement requests).
Also given that it's Google we are dealing with here, they probably save every single image generated (or at least its neural hash) and tie it to your account in their database.
The README itself reads like unedited AI output with several layers of history baked in.
- V1 and V2 appear in tables and diagrams but are never explained. V3 gets a pipeline diagram that hand-waves its fallback path.
- The same information is restated three times across Overview, Architecture, and Technical Deep Dive. ~1600 words padded to feel like a paper without the rigor.
- Five badges, 4 made up, for a project with 88 test images, no CI, and no test suite. "Detection Rate: 90%" has no methodology behind it. "License: Research" links nowhere and isn't a license.
- No before/after images, anywhere, for a project whose core claim is imperceptible modification.
- Code examples use two different import styles. One will throw an ImportError.
- No versioning. If Google changes SynthID tomorrow, nothing tells you the codebook is stale.
The underlying observations about resolution-dependent carriers and cross-image phase consistency are interesting. The packaging undermines them.
Oh hey, neat. I mentioned this specific method of extracting SynthID a while back.[1]
Glad to see someone take it up.