Is there an official llms.txt validator?

There is no official llms.txt validator. llmstxt.org publishes the proposal and a reference parser, but no body certifies files. This validator checks the documented structure and whether each link responds.

Is llms.txt a standard?

llms.txt is not a standard. It is a proposal published by Jeremy Howard of Answer.AI in September 2024, with no standards body behind it and no confirmation from major AI providers that they read it.

What does an llms.txt file look like?

A minimal llms.txt file has a title line such as # Example Co, a summary line such as > Accounting software for small agencies, and a section such as ## Docs followed by link lines like - [Quick start](https://example.com/docs/start): set up in ten minutes.

Do the links in llms.txt have to be absolute URLs?

In practice, links in llms.txt should be absolute URLs. The proposal defines no base URL, so a reader that fetched only the file cannot resolve a relative path. Write full https:// addresses.

Does llms-full.txt follow the same format?

llms-full.txt uses the same H1 and section structure as llms.txt, but contains the full text of each page instead of links to it. Link checks matter less there, and file size matters much more.

Free tool

LLMs.txt Validator

Validate llms.txt and llms-full.txt against the proposed format, line by line.

How it works

What is the LLMs.txt Validator?

The LLMs.txt Validator is a free tool that checks an llms.txt or llms-full.txt file against the llmstxt.org format. It looks for the required H1 title, the summary blockquote and H2 link sections, tests whether every link in the file responds, and gives a score out of 100 with the problems to fix.

How to use the LLMs.txt Validator

Enter a website to fetch its live file, or leave it empty and paste the file into the box below. Add the website with a pasted draft so relative links can be tested.
Choose the file to check: llms.txt or llms-full.txt.
Press Validate LLMs.txt.
Read the verdict and score out of 100, then the five-part summary: Markdown format, H1 title, quote block, project details and H2 file lists.
Check the details for any link that did not respond, each listed by URL, and the suggestions. The Formatted Preview tab shows the file that was checked.

What is the llms.txt format?

An llms.txt file is markdown in a fixed order. First an # H1 naming the project, which is the only required element. Then an optional > blockquote with a one-line summary, then any amount of plain prose with no headings. Then ## H2 sections, each holding a list where every item is - [Name](url), optionally followed by : description.

One heading has a reserved meaning. An H2 named ## Optional marks links a reader can skip when it is short on space. Anything outside this shape is still valid markdown, but a parser following the proposal ignores it.

What makes an llms.txt file fail validation?

A missing H1 fails the file outright, because it leaves a reader with nothing to call the site. So does any link that does not respond: this validator sends a request to every link and lists each one that fails or times out. A missing summary or missing H2 sections passes with a warning.

Write every link as [Name](url), because that is how the format marks a link, and a bare URL in plain text is not one. To test relative links such as /docs/start, enter your website so the validator can resolve them against it.

How do I test my llms.txt before publishing?

Paste the draft with your website filled in, so the validator can resolve and test every link. Fix what it reports, publish the file, then run it again with only the website to check the live copy.

The live run confirms the file is reachable at the root, because the validator reports an error when the file does not load. Also open the file in a browser and confirm you see plain text rather than a styled page.

Questions

Is there an official llms.txt validator?: There is no official llms.txt validator. llmstxt.org publishes the proposal and a reference parser, but no body certifies files. This validator checks the documented structure and whether each link responds.
Is llms.txt a standard?: llms.txt is not a standard. It is a proposal published by Jeremy Howard of Answer.AI in September 2024, with no standards body behind it and no confirmation from major AI providers that they read it.
What does an llms.txt file look like?: A minimal llms.txt file has a title line such as # Example Co, a summary line such as > Accounting software for small agencies, and a section such as ## Docs followed by link lines like - [Quick start](https://example.com/docs/start): set up in ten minutes.
Do the links in llms.txt have to be absolute URLs?: In practice, links in llms.txt should be absolute URLs. The proposal defines no base URL, so a reader that fetched only the file cannot resolve a relative path. Write full https:// addresses.
Does llms-full.txt follow the same format?: llms-full.txt uses the same H1 and section structure as llms.txt, but contains the full text of each page instead of links to it. Link checks matter less there, and file size matters much more.

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