Watermark
A visible or invisible marker embedded in media to signal origin or ownership. In AI, invisible watermarks like Google's SynthID tag generated images and video at the pixel level so software can later verify the content was AI-made — even after resizing or mild edits. Visible watermarks (logos, text overlays) also appear on stock imagery and some AI outputs. Why it matters: platforms and regulators increasingly require AI-content labeling, and watermark detection is becoming standard. Prompting note: watermark is also a classic negative-prompt entry to keep fake stock-photo marks out of generations.