Google has opened synthid.com to the public for free. Upload a photo, video or audio file and it checks for an invisible watermark that AI tools such as Nano Banana, Veo and Gemini embed when they generate content. It is English-only for now. Also works inside the Gemini app, Chrome and Google Search. Limit: a "no watermark found" result does not prove a file is real, because many AI tools do not add SynthID. Useful for checking product images, fake reviews or suspicious payment-slip or ad media, but do not treat it as conclusive evidence.