How to tell if an image was made with Flux

What Flux writes into the file

Flux is available through the Black Forest Labs API, through other providers' services and as open models you run yourself. The traces differ by route.

C2PA (Content Credentials) is a signed provenance record in the file, IPTC Digital Source Type a metadata field on how the image was made, for example trainedAlgorithmicMedia for fully AI-generated images. An invisible watermark sits in the pixels, and only the vendor can read it.

How to check a Flux image

1. Drag the original file from Flux into the box above. It is read in your browser, not uploaded. Screenshots and copies from stores or social networks usually no longer carry the data.
2. For images from the Black Forest Labs API or from fal.ai, the checker shows the C2PA record under “Content Credentials (C2PA)”.
3. For images from the FLUX.1 reference code, the checker shows Software “AI generated;txt2img;flux” and Make “Black Forest Labs” under EXIF and flags an AI hint.
4. If Flux ran in ComfyUI or AUTOMATIC1111, you find the prompt and settings in the PNG fields, as with Stable Diffusion.

More detail in the AI image checker and Content Credentials viewer and Prompt reader.

The checker is not an AI detector. It only shows what the file says. An empty result does not prove a real photo, not least because providers of AI systems placed on the market before 2 August 2026 have until 2 December 2026 to add machine-readable marking (Article 111(4) AI Act).

What survives uploads and edits

According to fal.ai, metadata can be lost through editing, re-saving or compression. That applies to every route.

Many services offer Flux, such as Replicate, Together AI, Mistral Le Chat or Freepik. Their documentation does not say whether they pass on the Black Forest Labs C2PA record or add anything themselves.

Labelling duty in your store under the EU AI Act

If you use Flux to create or edit images for your own store, you are a deployer, even when an agency or an employee works on your instructions (Article 3(4) AI Act, Commission guidelines para. 12, 14). If the image is a deep fake, meaning realistic and falsely appearing authentic, you have had to label it visibly since 2 August 2026 (Article 50(4) AI Act). The labelling check tells you whether that applies, and the guide to the labelling duty explains the rules.

The traces in the table do not replace that label, because people cannot see them straight away (guidelines para. 117). Still, keep them in the file, as the guidelines recommend. They document where the image came from.

How Flux labels its own output

Black Forest Labs relies on C2PA metadata in its API and recommends that developers using the open models add their own provenance data such as C2PA. This is stated in the model cards, not in the API developer documentation.

fal.ai checks its own signature and watermark at fal.ai/verify. None of the routes documents a visible mark on the image.