AI Crawler User-Agent Tokens in robots.txt vs ai.txt
The map lists them as complementary: sites and agents commonly implement both.
| AI Crawler User-Agent Tokens in robots.txt | ai.txt | |
|---|---|---|
| Lifecycle step | 3 Permit: What may the agent do here? | 3 Permit: What may the agent do here? |
| Answers | Which named AI crawler or agent user-agent tokens may a website allow or disallow in robots.txt, and what does each token actually control (search indexing, AI training, or live user-triggered fetches)? | May AI systems train on, scrape, index, or cache this site's content, and under what per-agent or per-path conditions? |
| Governed by | No single governing body; each vendor unilaterally defines and documents its own token(s); RFC 9309 (IETF, Standards Track) governs the underlying robots.txt syntax all of them use | None; at least three independent proposals for the same policy-declaration purpose (an IETF Internet-Draft by 'car', kaylacar/ai-txt, and an arXiv DSL paper) plus a fourth, differently-scoped product (aitxt.ing) all use the same filename with no shared authority |
| Status (issuer's words) | A convention, not a formal spec; each vendor's documentation is normative only for that vendor's own crawler | IETF Internet-Draft (draft-car-ai-txt-wellknown-00) presented as a formal well-known-URI registration proposal; kaylacar/ai-txt separately claims IANA filing (#76/#77, 'under review') |
| Version | Ongoing; tokens and their scopes are updated by each vendor independently | draft-car-ai-txt-wellknown-00 |
| Form / transport | well-known file | well-known file |
| Found at | /robots.txt | /ai.txt or /.well-known/ai.txt (varies by proposal) |
| Implementation | multi-implementation | prototype |
| Evidence | 5 verified, 1 reported | 3 verified, 1 thin |
| Primary use case | Control AI crawling and training use | Control AI crawling and training use |
| Last verified | 2026-10-23 (current) | 2026-10-23 (current) |
| Specification | https://www.rfc-editor.org/rfc/rfc9309.html | https://www.ietf.org/archive/id/draft-car-ai-txt-wellknown-00.html |
When to use which
- Choose AI Crawler User-Agent Tokens in robots.txt when your question is “Which named AI crawler or agent user-agent tokens may a website allow or disallow in robots.txt, and what does each token actually control (search indexing, AI training, or live user-triggered fetches)?” and you accept its maturity: status "A convention, not a formal spec; each vendor's documentation is normative only for that vendor's own crawler", implementation multi-implementation.
- Choose ai.txt when your question is “May AI systems train on, scrape, index, or cache this site's content, and under what per-agent or per-path conditions?” and you accept its maturity: status "IETF Internet-Draft (draft-car-ai-txt-wellknown-00) presented as a formal well-known-URI registration proposal; kaylacar/ai-txt separately claims IANA filing (#76/#77, 'under review')", implementation prototype.
Read the full articles
- AI Crawler User-Agent Tokens in robots.txt: Which named AI crawler or agent user-agent tokens may a website allow or disallow in robots.txt, and what does each token actually control (search indexing, AI training, or live user-triggered fetches)?
- ai.txt: May AI systems train on, scrape, index, or cache this site's content, and under what per-agent or per-path conditions?