Google’s SynthID system was recently used to identify and debunk a high-profile AI-generated hoax image. Earlier this week a photo circulated online that appeared to show Kentucky Senator Mitch McConnell connected to tubes and in severe distress in a hospital bed. The image was widely shared on Reddit and X, but by Wednesday the fact-checking site Snopes determined the picture contained the SynthID watermark designed by Google, showing it was AI-generated.
What is SynthID and how does it work?
SynthID was introduced at Google’s I/O developer conference in 2025. The system embeds an invisible signature (watermark) into AI-generated images that SynthID algorithms can detect while remaining imperceptible to casual viewers. Because the signature is encoded into the image itself, it survives even when images are screencaptured and reposted across multiple platforms, as happened with the McConnell image.
Limitations and participating providers
The main limitation of SynthID is that it only applies when an image-generation tool opts into the program. Google’s Gemini models have included the watermark since the program’s 2025 launch. OpenAI joined the initiative in May 2026 as part of a broader effort to combat malicious image generation. Anthropic does not participate in the program.
How users can check images
Users can check whether an image contains the SynthID watermark by asking a Gemini model or by uploading the image to OpenAI’s public image verification tool. The McConnell case demonstrates that the watermark can work in practice to halt the spread of a deceptive claim, but the system’s overall effectiveness depends on how widely image-generation providers adopt the program.
Context: McConnell’s health
Senator Mitch McConnell’s health has been the subject of intense speculation since he was taken to hospital after an emergency call on June 14. He has been largely out of the public eye since then, which has fueled conjecture about his condition. In this instance, however, the visual evidence circulating online proved to be entirely fabricated and was disclosed as such thanks to the SynthID watermark.
