SynthID detector: what’s possible

SynthID in one paragraph

Google DeepMind introduced SynthID in 2023 to watermark images from its Imagen model, and has since extended it to video (Veo), music and speech (Lyria and other audio models) and text (Gemini). The watermark is embedded by a neural network during generation and is invisible to people. A matching detector network can later recognise it, even after the content has been cropped, compressed or re-recorded. The detector is the part Google keeps to itself.

What GPTTrace checks instead

Google rarely relies on SynthID alone. Its products also write standard metadata, and that metadata is open to everyone:

• IPTC digital source type. Google labels AI images with trainedAlgorithmicMedia, which many apps display as “Made with Google AI”. GPTTrace reads it and treats it as proof.
• Content Credentials. As a C2PA steering member, Google has been adding signed manifests to content from its products. GPTTrace reads the signer and the actions.
• Visible marks. Consumer Gemini images and Veo videos have carried small visible watermarks; a suspiciously cropped corner is a hint.

When the metadata has been stripped, GPTTrace’s neural classifier and forensic checks examine the content itself, independent of any watermark. Those checks work on images from any generator, not only Google’s.

A practical approach

If you suspect an image, clip or song came from a Google model, run it through GPTTrace first: if the IPTC label or a Google-signed credential is present, you have your answer in seconds without uploading anything. If not, use Google’s own SynthID verification for a definitive yes or no on Google content, and treat the GPTTrace classifier result as the general-purpose check for everything else.

The bigger lesson is that watermarks and labels only cover the companies that use them. Open-source models running on someone’s own computer add neither, which is why content analysis remains necessary.

Why this page doesn’t pretend

Search for “SynthID detector” and you will find sites that claim to detect it. They can’t, unless they are Google. We would rather explain what is actually possible and give you the checks that do work, than show a fake “SynthID: not found” that would mislead you into trusting an image.