September 17, 2026 · 6 min read
How to Tell If an Image Was Made With Gemini (SynthID)
Check whether an image came from Google Gemini: SynthID watermark vs C2PA metadata, how to verify in the Gemini app, and what a metadata checker can show.
Google's Gemini image models (including the ones nicknamed Nano Banana) can produce very realistic pictures, so it's reasonable to want to check where an image came from. There are two different signals involved, and they need different tools. Here's how each works and which one you can actually check.
Signal 1: SynthID, the invisible watermark
Google DeepMind's SynthID embeds a watermark directly into the pixels of images made or edited with Google's AI. You can't see it, and it's designed to survive common changes like cropping, compression and screenshots. Because it's in the pixels, not the file's metadata, no metadata tool (including Skrubly's) can detect it. Detection needs Google's own tools.
Signal 2: C2PA Content Credentials (metadata)
Google has also started adding C2PA Content Credentials to images from its newer image models in the Gemini app and some Google Cloud products. According to Google's documentation, these credentials are signed by Google and name the Google service that produced the file. Unlike SynthID, this information lives in the file's metadata, so it can be read by a metadata checker, and it can be lost when a file is screenshotted, re-saved or uploaded to a platform that strips metadata.
| Check | What it finds | Survives screenshots/re-uploads | Tool |
|---|---|---|---|
| SynthID | Google AI watermark in pixels | Designed to | Gemini app verification |
| C2PA Content Credentials | Signed record of AI generation | Often lost | Metadata/C2PA checker |
| Visible watermark | Gemini sparkle logo on some images | Easy to crop out | Your eyes |
| Visual clues | Odd text, hands, reflections | Yes | Careful inspection |
How to verify in Gemini
At the time of writing, Google's help centre describes a verification feature built into the Gemini app and gemini.google.com:
- Step 1 — Open Gemini and add the image file.
- Step 2 — Ask something like: Was this created or edited with Google AI?
- Step 3 — Gemini checks for SynthID. If it finds it, all or part of the image was made or edited with Google AI.
- Step 4 — If no watermark is found, the image wasn't made with Google AI, but it could still come from another AI tool.
Google notes limits: the check only recognises Google AI content, there are daily usage limits, results can be unclear for small or lightly edited images, and screenshots should be cropped tightly around a single image. Google has said it plans to bring this kind of verification to more of its products, so the exact options may change.
Check the metadata with the AI Image Checker
If you have the original file, Skrubly's AI Image Checker reads C2PA Content Credentials and generator tags in its metadata. If a Gemini image still has its credentials, you'll see them. It runs in your browser, so the image isn't uploaded. What it can't do: detect SynthID, or tell you anything when metadata has been stripped. No markers means no markers, not proof the image is real.
Read an image's Content Credentials and AI generator tags.
Open the AI Image CheckerA sensible order of checks
- Find the earliest, highest-quality copy of the image you can, not a repost.
- Run it through a metadata checker for Content Credentials.
- Upload it to Gemini to check for SynthID.
- If it's from another AI tool, check that company's verification options (OpenAI has its own).
- Look for context: who posted it first, whether reputable sources confirm the event.
- Treat visual clues as hints only. Newer models make far fewer obvious mistakes.
More ways to judge whether a photo is real.
How to tell if an image is AIWhy no single check is final
Each signal answers a narrow question. SynthID tells you about Google AI and some partners, not every generator. C2PA tells you what a file says about itself, if the data is still there. Visual inspection is subjective. Put together with where the image came from, they give you a reasonable judgement, not certainty. Be especially careful before accusing someone of faking an image based on one tool's result.