About the llms.txt Validator
Because llms.txt is plain Markdown, small mistakes are easy to miss: a missing H1, a summary that is not in a blockquote, links written without proper Markdown syntax, or relative URLs that only make sense on your own site. This llms.txt validator fetches /llms.txt from a public domain, or accepts pasted text, and checks it against the proposed format from llmstxt.org.
It confirms there is exactly one H1 title, a summary blockquote, H2 section headings, correctly formatted Markdown link lists and absolute URLs, and reports anything that does not fit. Fix the issues in your file and re-run the check. A valid file is not a ranking signal, since llms.txt remains an optional proposal, but if you publish one it should at least be readable by the tools that support it.
How to use it
- Enter your domain to fetch /llms.txt, or paste the file contents.
- Run the validator to check structure and link syntax.
- Review errors for the H1, summary, sections and URLs.
- Correct the file, upload it again and re-validate.
Frequently asked questions
Where should llms.txt be located?
The proposal places it at the root of your site, at /llms.txt, similar to robots.txt. It should be served as plain text or Markdown with a 200 status. If your site lives in a subfolder, the proposal allows a path-level file, but the root location is the one tools are most likely to check.
Why must links in llms.txt be absolute URLs?
AI tools may read the file outside the context of your website, for example after fetching it into a conversation. Relative links such as /pricing cannot be resolved there, while https://example.com/pricing always works. Absolute URLs remove ambiguity for any tool that processes the file.
What is llms-full.txt?
llms-full.txt is a related convention, used by some documentation platforms, where the full text of key pages is combined into one Markdown file rather than just linked. It is not part of the core llms.txt proposal's required structure. It can be large, so publish it only if it is useful for your audience.