SynthID for video and audio: what exists, where to check, and why image checkers do not cover it
Google says SynthID watermarks video and audio as well as images, and it offers checks in its SynthID Detector and in the Gemini app. They find only media from Google and a short list of partners. Our checker reads still images only, so a video or audio file reads "Unable to check this file".
Does SynthID cover video and audio?
Yes, according to Google. Its SynthID Detector page says the watermark is built into the content itself: into the pixels for images and video, and into the frequency components of audio. In a post dated October 7, 2026 (updated October 29), Google says it has watermarked over 180 billion images and videos, along with 240,000 years of audio content.
The same post says anyone can use the SynthID Detector, available globally in English, to check an image, video or audio file. It says the tool finds media made with AI from Google or its partners, and it names OpenAI, NVIDIA, Kakao and Apple. Google's post of May 19, 2026 adds that Google is partnering with NVIDIA to watermark AI-generated video from its Cosmos models.
Where can I check a video or audio file for SynthID?
As of October 30, 2026, the places below are the ones the companies' own pages describe.
| Where | Video | Audio | Limits stated |
|---|---|---|---|
| Google SynthID Detector (synthid.com) | MP4, MOV, WEBM | WAV, MP3, OGG, FLAC, AAC, M4A | Finds only media from the companies it lists; the page says it is not a general AI detector. |
| Gemini app and gemini.google.com | Under 90 seconds each | Under 1 hour each | One file at a time, 100 MB or less. A signed-in personal or qualified Workspace account. About 10 video checks (up to 5 minutes in total) and 10 audio checks (up to 3 hours in total) in any 24-hour rolling window. |
| OpenAI Content Provenance API | No video check is listed | MP3, Opus, AAC, FLAC, WAV, PCM | 50 MiB per file; audio of 60 seconds or less after decoding. Checks only for supported OpenAI signals; for audio, that is a SynthID watermark. |
The details come from Google's Gemini help page on verifying images, videos and audio, the synthid.com page and OpenAI's content provenance guide. Quotas and limits change, so read those pages on the day you check.
Google's May 19 post says SynthID verification for image, video and audio was added to the Gemini app first, then to Search that day, with Chrome over the coming weeks. Its October 7 post lists Search, the Gemini app and Chrome as having built-in verification.
Whose video and audio can these checks recognize?
Only media from the companies that use SynthID. The synthid.com page says the tool can only detect media from the companies it lists. Google's Gemini help page says Gemini recognizes content created by Google's own AI tools, even though other companies have started to adopt SynthID.
The company lists differ by page. On October 30, 2026 the synthid.com page showed Google, NVIDIA, OpenAI and Kakao. Google's October post also names Apple, so we write that Apple is a partner according to Google. OpenAI's guide says its own tool does not detect content made by another company's model.
What does a SynthID result for a video or audio file mean?
Gemini's help page describes its results for images and video. It says that a detected watermark means all or part of the video was created or edited by Google's AI models. For video, Gemini states which parts carried the watermark. It adds that this does not mean every moment of that part has it. It does not spell out audio results; synthid.com says its detector finds audio segments with the watermark.
A missing watermark is weaker. Gemini says a video without one was not created or edited by Google AI, but could have been created by other AI systems. It also says some results are unclear, for example when the content is very simple or abstract, or the edit is small. The synthid.com page adds that heavy compression and editing can hide the signal, and that in very rare cases it can trigger on content that was not watermarked.
Google's Gemini help page says the watermark will usually still exist after a video or audio file is re-scaled, re-colored or compressed, but after many changes it may not be detected. OpenAI's guide says a result of not detected is an absence of detected evidence, not proof that someone made the content by hand.
Why does an image checker not cover video and audio?
Our checker opens six image types: JPEG, PNG, WebP, AVIF, HEIC and GIF. It reads the file's own bytes to decide, not the file name. A video or an audio clip is none of those, so it stops before any check runs. Even for images, our checker does not look for SynthID.
Our measured result: on October 30, 2026 we made three tiny files with ffmpeg and put each in the checker. One was a 1 second MP4 (H.264 video and AAC audio). One was a 1 second QuickTime MOV with the same streams. One was a 1 second WAV tone. All three read "Unable to check this file", with the line "This is not an image format the checker reads (JPEG, PNG, WebP, AVIF, HEIC, GIF)." No check ran, and no preview or finding was shown.
Four other files read the same: a PDF, an SVG, an empty PNG, and a text file named .jpg. Our accuracy page shows our other measurements.
One limit matters. We made these clips ourselves, and they carry no SynthID watermark, no Content Credentials record and no other mark. The test shows what our checker does with a video or audio file. It says nothing about whether any real video or audio file carries a watermark.
What this means when you check an image
Open the checker and choose a file. If it is a video or an audio file, you will see the headline "Unable to check this file". It means the file is not one of the image types we read. It tells you nothing about whether the file has a watermark or a provenance record.
If the video or audio might come from Google or one of its partners, use the maker's own tool. Google's SynthID Detector and the Gemini app take video and audio. They open another company's site, you may need to sign in, and your file goes to them, not to us. Our Privacy and method page explains what our checker does with a file.
Finding nothing does not mean a file is real or made by a person.
Guides on this topic
- What is SynthID? is the main page on this topic.
- Google's SynthID checks in Gemini, Search and Chrome covers the image side of the same tools.
- Does OpenAI use SynthID? covers what OpenAI's checker reads.
- Invisible AI watermarks compared sets SynthID beside the other marks.
- Do Gemini and Nano Banana images carry SynthID or Content Credentials? covers Google's own images.
Frequently asked questions
- Can I check a video for SynthID?
- Google says you can, in its SynthID Detector or in the Gemini app. Gemini takes videos under 90 seconds, one file at a time. The detector recognizes only media from Google and its partners.
- Does OpenAI's check cover video?
- OpenAI's API guide lists images and audio. It describes no video check, and it says the tool looks only for OpenAI's own signals.
- Does "not detected" mean a video or audio file is real?
- No. Google says a file without the watermark could still come from other AI systems, and that heavy editing can hide the signal. The result speaks only to SynthID.
- Can your checker read the audio of a video file?
- No. It reads still images only, so an MP4, a MOV or a WAV file reads "Unable to check this file".