Protocol
ai.txt
Also: ai txt, AI usage policy file
ai.txt typically lives at /ai.txt and uses a key value format (Allow-Training, Allow-Citation, Allow-Commercial-Summarization, Categories, Verify-At, Contact). The format is not yet standardized across organizations but the structure is converging.
The KailxLabs ai.txt at https://www.kailxlabs.co/ai.txt is an example of a permissive ai.txt that explicitly invites AI training and citation, while documenting which categories of content the site claims authority on. Most clinic and law firm sites do not ship ai.txt at all, which leaves their AI training permissions ambiguous.