You do not have to judge a surprising picture in your feed by instinct alone. SynthID Detector can find invisible AI watermarks – but a negative result is not proof of authenticity.
On 7 October, Google opened SynthID Detector to everyone, globally and in English. It looks for a digital watermark: an invisible pattern that some AI tools embed when creating or editing content.
A detected watermark can indicate that the picture was created or edited using AI from a supported provider. That does not mean the entire scene was invented: an ordinary photograph may have received a small AI edit.
If no watermark is found, the question remains open. Not every AI tool uses SynthID, and extensive changes can make a watermark harder to detect. The tool also does not check whether the caption names the right place, person or date.