Three years ago, Google introduced a watermarking system for AI-generated content called SynthID. Nobody was required to use it. It was just Google's answer to a problem the rest of the industry hadn't fully admitted existed yet. Now OpenAI is using it. So is Nvidia. So are ElevenLabs and Kakao. And Google says SynthID has already been applied to 100 billion images and videos, plus 60,000 years worth of audio. The timing matters. AI-generated images and video have gotten good enough that the old tells, the extra fingers, the smeared text, the wrong shadows, are mostly gone. What replaces them as a detection method isn't human judgment. It's watermarking inserted into the content at the point of generation, before it ever reaches anyone's feed. SynthID is Google's bet on how that works at scale, and a growing number of the industry's biggest names are now betting alongside it.