A PNG file has places for text as well as the picture. Many AI tools note how an image was made there, so a PNG as first received is often decisive evidence on its own.
tEXt and iTXt chunks store the prompt, negative prompt, seed, sampler, model name and node workflow. Some services also write an AI-generated digital source type into XMP. Origma reads these fields and records which keys were present in the ledger.
A generating tool's work record is hard to produce by accident, so it is strong evidence. It is still plain text anyone could write, so if it conflicts with the pixel detectors the conflict is shown as well.
Conversion to JPEG or WEBP, messenger and social uploads, image optimisers and screenshots mostly remove these fields. Erased copies are judged by the detectors, so the same picture can rest on different evidence.
Do not re-save the PNG; scan it as received. If record keys appear in the ledger, that is strong evidence the file came from a generating tool; if not, read the detector result as a range.
This is general guidance, not legal advice. A scan result is a probabilistic assessment, not proof.