What it is
DeviantArt introduced the noai and noimageai directives to communicate that artwork is not authorized for use in third-party AI datasets unless the creator opts in. The project is notable because it paired policy defaults with concrete HTML meta tags and HTTP headers that other platforms could reuse.
Evidence trail
Examples
HTML robots meta tags Source
DeviantArt's team announcement publishes these exact page-level directives for opted-out artwork.
<meta name="robots" content="noimageai">
<meta name="robots" content="noai"> HTTP response headers Source
The same announcement says DeviantArt sends these directives when the image file is downloaded directly.
X-Robots-Tag: noimageai
X-Robots-Tag: noai