What opened
Google opened SynthID Detector to the public on 7 October, a year and a half after releasing an early version to journalists and researchers on a waitlist. The tool now sits at synthid.com, available worldwide, in English only.
Anyone can upload an image, a video or an audio file and be told whether it carries a SynthID watermark — the imperceptible signal Google has been embedding in output from its own generative models since 2023.
The numbers Google gave
Pushmeet Kohli, Google DeepMind’s vice-president for science and strategic initiatives, wrote that more than 180 billion images and videos have been watermarked with SynthID since launch, along with more than 240,000 years of audio.
Google also says the verification built into Search, the Gemini app and Chrome handles more than a million requests a day between them. That figure covers the integrated features, not the standalone detector, which had no published usage number of its own.
TechCrunch lists the formats: JPG, PNG, WEBP, AVIF, HEIC, TIFF, GIF and BMP for images; MP4, MOV and WEBM for video; WAV, MP3, OGG, FLAC, AAC and M4A for audio. Google watermarks media from its Nano Banana, Veo and Lyria models and from products including Gemini, Flow, ProducerAI and Vids.
What it does not do
The limit is the whole story. SynthID Detector is not an AI detector. It checks for one company’s watermark and the watermarks of the partners who have adopted it — OpenAI, Nvidia and Kakao, with Apple described as joining soon. Anything generated by a model outside that group comes back unmarked, which is not the same as coming back human.
That gap is not theoretical. Reuters reported in July that Meta’s own AI image detector failed to identify some of its own cropped AI images. A watermark survives what the format and the detector were designed to survive, and not reliably more.
Why the partner list is the real question
A provenance signal is worth what its coverage is worth. One company checking its own output tells a reader almost nothing about a file from somewhere else; a signal that most large generators carry starts to mean something when it is absent.
Google’s partner list is the asset here rather than the detector interface. OpenAI maintains its own verification site separately, and Microsoft and Meta run their own watermarking standards, so a reader who wants certainty about an arbitrary file still has to know which tool to ask.
What to watch
Three things. Whether Apple actually ships SynthID support and on what. Whether the detector gets languages beyond English, given that Google has launched it globally. And whether anyone publishes false-negative rates for watermarks that have been cropped, re-encoded, screenshotted or run through a filter — the ordinary handling that happens to every image on its way across the internet.
