llms.txt Checker

llms.txt is a proposed standard (spec at llmstxt.org) for a markdown file at your site root that gives AI assistants a curated index of your most useful pages. It opens with an H1 project name, a blockquote summary, and H2 sections listing links in the form "- [Title](url): notes". It is not a robots.txt - it grants no permissions and blocks nothing. It is a reading list.

Both - the terms are used interchangeably for this file, and this page does what all three names imply. It fetches the live file (a tester), checks it against the llmstxt.org format (a validator), and reports what is missing or malformed (a checker). Every finding is labelled with its source, so you can see which rules come from the spec and which are LintPage recommendations that a valid file can ignore.

Almost always because a catch-all route is serving your application shell. Single-page frameworks answer any unmatched path with index.html and a 200 status, so /llms.txt "exists" in the sense that something came back - it is just your HTML. A model fetching that file gets a page of markup and no index. This tool checks the body, not just the status code, which is why it catches what a plain existence check cannot.

There is no confirmed evidence that any major AI assistant reads llms.txt to decide what to retrieve or cite today. Adoption is growing, the file is cheap to add, and it costs you nothing if it turns out to matter later - but anyone telling you it improves your AI visibility right now is guessing. If you are adding one, add it because you want a curated index to exist, and make it well-formed.

llms.txt is an index: links and one-line notes, small enough for a model to read in full before deciding what to fetch. llms-full.txt is the expanded version - the actual content of those pages concatenated into one file. If your llms.txt has grown past a few dozen kilobytes, the content in it belongs in llms-full.txt, and the index should go back to being a list of links.