Metadata is not only an EXIF thing

Most metadata advice is written for JPEG and talks entirely about EXIF. PNG does not use EXIF the same way, and PNG has its own place to hide text: a chunk type built into the format for exactly that purpose. Following JPEG advice on a PNG file can leave the text chunks untouched while you believe the file is clean.

What a chunk actually is

A PNG file is a sequence of labelled chunks - blocks of data each tagged with a four-letter type. Pixels live in IDAT chunks. Text lives in tEXt, zTXt and iTXt chunks, which any encoder is free to write and most viewers never show you. The format was designed to carry a keyword and a string: Author, Description, Software, or anything else a tool decides to put there.

Where the text comes from

Screenshot tools on some platforms write the source app into a chunk. Editors write their own name and version. The case worth knowing about specifically: image-generation tools frequently write the entire prompt, seed and model name into a tEXt or iTXt field, because that is genuinely useful for anyone trying to reproduce the image later. Some of these fields overlap with the newer, more formal effort to standardise provenance metadata across formats, a subject covered in content credentials and provenance tags. None of that is visible in the picture. It sits in the file next to the pixels, and a normal viewer shows you the second and hides the first.

Why it matters for an upload

If you save a screenshot of a result page, crop an image in an editor that stamps its own field, or re-export through a tool that copies chunks forward, that text rides along. It is a smaller exposure than a GPS coordinate, but it is not nothing: it can name the software you used, and in the generation case, describe exactly what was asked for. Stripping EXIF before you upload is the right habit for JPEG; it does not automatically touch a PNG's text chunks, because they are a different part of the format entirely. mogrify -strip and the Windows "remove properties" dialog both clear PNG chunks along with EXIF, which is one reason those general-purpose tools are worth using over anything format-specific.

Checking for yourself

Reading a photo's metadata before you upload it covers the general approach, and PNG chunks show up in the same inspection tools as everything else - exiftool lists them under different field names than JPEG's, but it lists them. Rating tools mostly do not care what software made your file; Rate Cock scores the pixels regardless of the container. What a service does with the file afterward is a separate question from what the model reads, and it is worth checking how any tool describes its handling of uploads generally - Penis Rater's comparison of tool practices treats this kind of detail as a real differentiator rather than boilerplate. The same caution applies to a file sent to a person rather than a model: what is worth including or leaving out for a human judge is its own small set of habits. Measurement tools receive photographs too, and their intake is no more exempt from carrying a stray chunk than a scoring tool's is - how Measure My Cock handles submitted images is worth a look for the same reason.