The tool, called SynthID, will initially be available only to users of Google's AI image generator Imagen, which is hosted on Google Cloud's machine learning platform Vertex.

Users will be able to generate images using Imagen and then choose whether to add a watermark or not. The hope is that it could help people tell when AI-generated content is being passed off as real, or help protect copyright.

Traditionally images have been watermarked by adding a visible overlay onto them, or adding information into their metadata. But this method is "brittle" and the watermark can be lost when images are cropped, resized, or edited.

Google DeepMind VP  Pushmeet Kohli said SynthID uses two neural networks. One takes the original image and produces another image that looks almost identical to it, but with some pixels subtly modified. This creates an embedded pattern that is invisible to the human eye.

The second neural network can spot the pattern and will tell users whether it detects a watermark, suspects the image has a watermark, or finds that it doesn't have a watermark.

Kohli said SynthID is designed in a way that means the watermark can still be detected even if the image is screenshotted or edited -- for example, by rotating or resizing it.