AI parameters in PNG files: the Stable Diffusion "parameters" chunk, ComfyUI workflows, and what they prove
Some Stable Diffusion tools write a prompt and settings into a PNG as plain text. AUTOMATIC1111's web interface uses a chunk named "parameters"; ComfyUI uses "prompt" and "workflow". Anyone can add, edit or delete such text, so it is a hint about a tool, not proof of how an image was made.
What is the "parameters" chunk in a PNG?
A PNG file is a series of chunks. Some hold the picture; others hold text. The PNG specification defines three text chunk types (tEXt, zTXt and iTXt) and lists them among its ancillary chunks, which a decoder may ignore. A tEXt chunk holds a keyword, such as "parameters", and a text string.
In its source file modules/images.py, the AUTOMATIC1111 web interface saves a PNG with a text entry whose keyword is "parameters". The value is the generation text the tool built for that image. The code does this only when a setting called enable_pnginfo is on. When it is off, no text chunk is written. The project's feature page describes the same behavior: generation parameters are added to the PNG as a text chunk.
For JPEG and WebP files, the same source uses an EXIF field called UserComment instead. Our PNG test below does not cover it.
What does ComfyUI write instead?
ComfyUI is a node-based tool. In its nodes.py, the save node adds a PNG text entry with the keyword "prompt", holding the job as JSON. It then adds one more text entry for each item the caller passes as extra information. Its disable_metadata argument skips both steps.
ComfyUI's workflow metadata page names the two keywords: "prompt" and "workflow". It says "workflow" holds the complete graph (nodes, links and layout) and that "prompt" holds the API prompt used to execute the workflow. A file may carry one without the other.
| Tool | PNG text keyword | What it holds | How a user leaves it out |
|---|---|---|---|
| AUTOMATIC1111 web interface | parameters | The generation text for the image | Turn off the enable_pnginfo setting |
| ComfyUI | prompt | The API prompt used to execute the workflow (JSON in the code) | Start with --disable-metadata, or use the desktop setting "Disable saving prompt metadata in files" |
| ComfyUI | workflow | The complete graph: nodes, links and layout | The same switch |
What did we find when we checked these chunks?
We drew two PNGs and added example text we invented. No real prompt and no real model is involved. One has a text chunk named "parameters", laid out in the style of the AUTOMATIC1111 interface: a prompt line, a negative prompt line and a settings line. The other has chunks named "prompt" and "workflow", in the style of ComfyUI. We measured both in Chrome on October 30, 2026.
Both read "Tool name found in metadata", at the tier we call Hint. For the first file, the finding says the keyword "parameters" names the Stable Diffusion family. For the second, it says "prompt and workflow" names ComfyUI. Both findings add that a name in metadata is a hint, not a declaration. Neither file has a signed record.
We also hold two real files that Wikimedia Commons files under Stable Diffusion. Third parties uploaded them, and we cannot know how each was handled before upload. Neither holds text of this kind. The PNG reads "No supported provenance signals found" and the JPEG reads "Metadata found; source not established", because it holds only an EXIF date. Counts for the whole test set are on our accuracy page.
These two small tests show how our checker reads the keywords, not how often real files carry them.
Does a parameters chunk prove an image came from Stable Diffusion?
No. Three reasons follow.
- The text is plain. The chunk is ordinary text with a keyword. We made our two test files by adding that text to a drawn picture. Anything that writes PNG text can do the same.
- The file's check value does not vouch for it. Every PNG chunk carries a CRC. The specification says it can be used to check for corruption. It detects damage; it does not show who wrote the text.
- It is not a signed record. A Content Credentials record is signed, and a checker can test whether the image still matches it. A text chunk has no signature at all.
The reverse also holds. A file without these chunks says nothing either way, because a user can turn the setting off.
Is a parameters chunk the same as the Stable Diffusion watermark?
No. The chunk is readable text that a tool writes when its setting is on. The Stable Diffusion watermark is a hidden pattern in the pixels; Stable Diffusion's reference script adds one with the invisible-watermark library. Our guide on the Stable Diffusion invisible watermark explains it. A file can carry one, both or neither.
What happens to the chunk when a file is shared?
ComfyUI's page says a copy keeps the text and a rewrite may remove it. We did not test these two files that way. In a separate test on October 30, 2026 we re-drew each of the 9 real files that carry a Content Credentials record on a canvas and saved them again. After the PNG re-save and after the JPEG re-save, 0 of 9 still read a record, and all 18 outputs read "No supported provenance signals found". That test used files with records, not text chunks, and it was a canvas in one browser, not a platform. Our guide on sharing and metadata goes further.
What this means when you check an image
Open the checker, choose the file, and look for the headline "Tool name found in metadata". It tells you the file's metadata names a tool, such as the Stable Diffusion family or ComfyUI. The line under it says there is no signed record and no source declaration. Treat it as a lead: ask where the file came from.
If the headline is "No supported provenance signals found", we found no signed record, no source label, no tool name and no Stable Diffusion watermark pattern. The line under it says this does not mean the image is real or human-made. The checker's fixed limits line applies in both cases: "These checks cannot determine whether an image is AI-generated."
Our rule for these chunks looks at PNG text keywords only. We have not tested the EXIF UserComment case, and the headline reports the tool named, not the prompt or the settings.
Guides on this topic
- How to tell if an image is AI is the main page on this topic.
- The Stable Diffusion invisible watermark covers the hidden pattern our checker can decode.
- Where AI declarations live in an image file maps the places a label can sit.
- Can EXIF data be faked? covers unsigned metadata.
- Does sharing an image remove its metadata? covers what happens in transit.
Frequently asked questions
- Can I read the prompt stored in a PNG?
- If the file still carries the chunk, AUTOMATIC1111's feature page says software that can view PNG chunk information can show it. Our checker reports the tool named in the file, not the text inside.
- Does ComfyUI always save the workflow in the image?
- No. ComfyUI's page says files created with
--disable-metadatado not contain the standard workflow metadata, and that a file may carry "prompt" without "workflow". - Does a missing parameters chunk mean the image was not made with Stable Diffusion?
- No. The setting can be off, and a re-save or an editor can remove the text. Finding nothing never shows that an image is real or human-made.
- Can someone add a fake parameters chunk?
- Yes. The chunk is unsigned text. We made our two test files that way, with invented example text.