Microsoft Paint and Photos Apps Found to Embed Invisible Watermarks in AI-Generated Images

A developer named Xusheng Li has discovered that Microsoft's Paint and Photos apps embed an invisible watermark in AI-generated images, in addition to a visible Copilot logo. This was revealed through reverse-engineering by Li, who found that the Paint app attaches C2PA Content Credentials to saved files and uses two functions: AddPerceptibleWatermark and WmkWriteWatermark. The latter appears to write the invisible watermark, which is required for image generation in Paint.

Li also discovered that Microsoft Photos uses a similar method of GUID watermarking with its AI tools. He suggested that this might be related to Article 50 of the EU AI Act, which requires AI-generated content to carry a detectable, machine-readable mark. This could mean that prompts are still sent to Microsoft servers for moderation even when image generation appears to happen locally on a device.

The discovery adds to the ongoing debate about how people and apps should identify AI-generated material. Watermarking is seen as a way to understand what you're looking at and where it came from, but some argue that it devalues the time, labor, and thought that artists put into their work.