The extension requests /llms.txt and checks the body against the format at
llmstxt.org. A file is flagged when:
the body is HTML rather than Markdown, which usually means a soft 404;
the body is under 50 bytes;
there is no H1 (a line starting with # ), which the format requires;
there are no Markdown links.
It also sends a HEAD request for /llms-full.txt and notes it if present.
That file is a common convention, not part of the llms.txt format, so it never
passes this check on its own.
llms.txt is widely published but has no confirmed consumer yet, so this is a
bonus check: it adds points when present and costs nothing when absent.
Results
Status
When
Pass
/llms.txt exists and has none of the problems above
Warn
/llms.txt exists but has one or more of the problems above
N/A
No /llms.txt was found
Unmeasured
The request failed with a server error or network error
How to fix
Publish a Markdown file at /llms.txt with an H1 naming the project and links
to your most important pages:
# Example Ltd> Accounting software for small businesses.
## Docs-[Getting started](https://example.com/docs/getting-started.md): Install and set up an account.
-[API reference](https://example.com/docs/api.md): Endpoints, authentication, and limits.
Announced means the vendor’s own docs or announcement say so. Published is the date on the vendor’s own page, where it has one. Checked is the last time our weekly research found that page still saying so.
No agent or browser has announced anything about this yet.
No evidence yet27
ChatGPT
Claude
Gemini
Perplexity
Copilot
Meta AI
ChatGPT Atlas
Comet
Dia
Gemini in Chrome
Edge Copilot Mode
Claude Code
Cursor
Codex
GitHub Copilot
Windsurf
CCBot
Applebot
Amazonbot
Bytespider
Cohere
Mistral
DuckAssist
Chrome
Edge
Firefox
Safari
Names and marks belong to their owners and are used only to identify products. None of these vendors is affiliated with Sitebulb. Spotted something out of date? Send a correction.
Adoption on the top 100 sites
28%
26 of 93 measured sites implement it
Scanned 23 Oct 2026 with the Sitebulb Labs extension, against the Tranco list (tranco-56Z8N). 7 sites couldn’t be measured (bot challenge or timeout) and are left out of the share.
Specified, but little evidence anything uses it yet.
How this rating is worked out2 of 9 points
Factor
Points
Why
Vendor support
0 / 3
0 vendors supporting, 0 partly or planned
Top-100 adoption
2 / 3
28% of measured sites
Spec maturity
0 / 3
Community proposal
8 or more points is Established, 5 to 7 is Gaining traction, 2 to 4 is Speculative and under 2 is Stalled. A feature is also Stalled when more vendors have said no than yes. Read the spec.
Community insights
Sceptical
After IP verification, 72% of bot-claimed llms.txt requests were spoofed. GPTBot is the only verified bot that fetched llms.txt more than once. The file’s primary audience is the SEO industry auditing whether the file exists.
It is free to produce, it hurts nothing, and a small share of its readers are real agents. But we stopped treating it as the destination and put the effort where the agents actually go.
Artur FerreiraFounder, The GEO LabOn their blog, 20 Jul 2026Website
Adam AltmanCEO and Founder, RedoclyOn their blog, 9 Sept 2026Website
Louise LinehanContent Marketer, AhrefsOn their blog, 15 Jun 2026Website
John MuellerSearch Advocate, GoogleOn Bluesky, 17 Jun 2025Bluesky