Reverse engineering reveals how Paint and Photos embed a server-issued GUID into the pixels of locally generated AI images.
TL;DR
  • Microsoft Paint supports both local and cloud image generation;
  • Paint and Photos also ship local AI models;
  • The two apps send the prompt to a remote server for moderation;
  • The server returns a GUID along with the moderated prompt;
  • The GUID is embedded into the locally generated image as an invisible watermark;
  • A separate visible-watermark setting does not control this invisible watermark;
  • On Copilot+ PCs, image generation is local but prompt moderation remains remote;
  • Microsoft discloses that Paint adds C2PA metadata to AI-generated images;
  • AI-generated image saves limited to C2PA-preserving formats: PNG, JPEG, GIF, and .paint .