How to Check a SynthID Watermark in Video for Free

On October 7, 2026, Google opened its SynthID Detector to everyone worldwide — a free tool that checks whether a video (or image, or audio clip) carries SynthID, the invisible watermark Google embeds in AI-generated media. Here’s exactly how it works, what it can and can’t tell you, and what to do when it finds nothing.

What Is SynthID, Exactly?

SynthID is Google’s system for watermarking AI-generated content, introduced in 2023 and expanded steadily since. When compatible Google AI tools generate or edit media — Veo video, Gemini images, Lyria audio — they embed an imperceptible watermark into the file. Invisible to the eye, inaudible in audio, but detectable by software.

Google says SynthID now marks more than 180 billion images and videos. The watermark is designed to survive common modifications — cropping, filters, and compression.

What the Public SynthID Detector Can and Can’t Check

It can:

• Check uploaded images, videos, and audio files for a SynthID watermark — for free, one file at a time.
• Break a video into its picture and audio tracks, highlighting which stretches carry a watermark.
• Deliver the verdict “made or edited with Google AI.”

It can’t:

• Prove a video is real. A “not detected” result only means no SynthID watermark was found.
• Check without signing in — you’ll need a Google, Apple, or OpenAI account.
• Scale to bulk checking — built for one file at a time.

How to check a SynthID watermark in video for free — Google SynthID Detector result screen

Step-by-Step: Checking a Video’s SynthID Watermark

1. Go to synthid.com. As of October 2026 the detector is open worldwide but in English only.
2. Accept the terms. This is a manual, one-file-at-a-time tool.
3. Sign in. Use a Google, Apple, or OpenAI account.
4. Upload the video file. Use the original file if you can.
5. Read the result. Either the watermark is detected (“made or edited with Google AI”) or it isn’t (“not detected”).
6. Interpret carefully. “Detected” = the video passed through a SynthID-watermarking AI tool. “Not detected” says nothing about whether the video is AI-generated.

The Big Limitation: Most AI Videos Have No Watermark

SynthID detection is a check for one specific watermark, not a universal AI test. Many AI tools add no watermark at all. A clean result from SynthID proves nothing.

• Positive result → strong evidence the video passed through Google’s or a partner’s AI tooling.
• Negative result → keep verifying. Run the video through a free AI video detector, inspect frames by hand, and reverse-search distinctive frames.

Layered video verification: SynthID watermark check plus artifact detection and reverse search

Frequently Asked Questions

Is Google’s SynthID Detector really free?

Yes. Since October 7, 2026, it’s open to everyone worldwide at synthid.com at no cost.

Can SynthID detect any AI video, like Sora or Runway clips?

No. It only detects SynthID watermarks. Videos from other generators carry no SynthID watermark.

Does a “not detected” result mean the video is real?

No. It means no SynthID watermark was found. The video could still be AI-generated.

Can the watermark be removed?

Google designed it to survive cropping, filters, and compression — but heavy compression or regenerating the file can weaken or remove it.

What’s the best free workflow for checking a suspicious video?

SynthID Detector (watermark check) + a free AI video detector (artifact check) + reverse image search + a source check.