llms.txt checker
The most thorough llms.txt validator on the web. 10 checks against the llmstxt.org specification — including the HTTP Content-Type header and the llms-full.txt companion file that most validators skip.
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What is llms.txt?
The llms.txt file is a markdown file served at /llms.txt that provides LLM-friendly content about your website. It acts as a machine-readable index, similar to how sitemap.xml works for search engines, but optimised for AI agents and language models.
Why should I add llms.txt to my site?
Without /llms.txt, LLMs have to scrape and guess at what your site is for, which hurts citation accuracy. With it, ChatGPT-style agents get a curated, link-rich index to the pages you actually want them to cite - cheaper than rewriting your whole site for LLM-friendly navigation, and the only standard currently in wide use across docs sites.
What does the llms.txt validator check?
Ten checks against the llmstxt.org spec:
- File is accessible at /llms.txt (HTTP 200)
- Starts with an H1 heading (project/site name)
- Contains valid, parseable markdown
- Has a blockquote summary below the H1
- Includes H2 sections with file lists
- Links use the correct [name](url) format
- Linked URLs are accessible
- Optional section format used correctly
- Content-Type is text/plain
- llms-full.txt companion is available
How does this compare to other llms.txt validators?
The llmstxt.org spec describes eight structural rules, plus implied HTTP semantics. Most validators in circulation — including llmstxtchecker.net — cover the structural rules and follow the linked URLs. Agent Ready does that too, and adds two checks the spec implies but most tools skip: the HTTP Content-Type header and the llms-full.txt companion file.
| Check | Agent Ready | Typical other validators |
|---|---|---|
| File accessible at /llms.txt | yes | yes |
| H1 heading present | yes | yes |
| Valid, parseable markdown | yes | yes |
| Blockquote summary | yes | yes |
| H2 sections with file lists | yes | yes |
| Link format [name](url) | yes | yes |
| Linked URLs return 200 | yes | yes |
| Optional section used correctly | yes | varies |
| Content-Type: text/plain | yes | rarely checked |
| llms-full.txt companion | yes | rarely checked |
| Folded into full agent-readability scan | yes | no |
Information based on the public copy at llmstxtchecker.net as of 2026-05-11. The Content-Type and llms-full.txt checks are part of our 10 llms.txt rules (see methodology); the full-site scan adds 49 more checks across page metadata, site discovery files, and agent-protocol manifests.
Minimal valid example
# Acme Cloud Widgets
> Widgets-as-a-service for serverless apps. Deploy in one command.
## Docs
- [Getting Started](https://acme.dev/docs/start.md): zero-to-deployed in 60s
- [API reference](https://acme.dev/docs/api.md): REST endpoints and auth
## Examples
- [Node.js quickstart](https://acme.dev/examples/node.md)H1 title, blockquote summary, H2 sections with [name](url) links. That’s the whole spec.