llms.txt Validator & Generator
Check any site's llms.txt — pasted directly or fetched live by URL — against the llmstxt.org specification: correct H1/blockquote/section ordering, valid link list syntax, duplicate section names, and the special meaning of an "Optional" section. Or generate a spec-conformant llms.txt from a simple form and copy the output. Paste mode runs entirely in your browser; URL fetch mode uses a rate-limited, SSRF-guarded server endpoint.
How to use
- Validate mode: paste llms.txt content directly, or enter a site's URL to fetch its live llms.txt and check it against the llmstxt.org spec.
- The validator checks the required order — H1 title, then an optional blockquote summary, then freeform details, then ## sections — and flags malformed link list items, duplicate section names, and content out of order.
- Generate mode: fill in a title, summary, optional details, and any number of ## sections with links, and copy the correctly formatted llms.txt output.
- A section named "Optional" has special meaning in the spec — its links can be skipped by a consumer that needs a shorter context, so use it for secondary resources.
Understanding the output
Parsing follows the llmstxt.org specification directly: only the H1 is strictly required, everything else is optional but must appear in the correct order when present. Errors mark spec violations (wrong order, malformed links, content outside a section); warnings mark things that are valid but likely mistakes (a missing blockquote, an empty section).
Common issues & tips
- •"That URL returned an HTML page, not a plain-text file": the URL fetch mode expects the raw llms.txt content — check the URL points directly at /llms.txt, not a page that links to it.
- •"Freeform text found inside or after a ## section": once a ## section starts, the spec only allows link list items inside it — move any prose above the first ## heading.
- •"Blockquote summary found out of order": a blockquote is only meaningful as the single summary immediately after the H1 — a blockquote used later (e.g. as a per-section subtitle) isn't part of the format's grammar.
Frequently asked questions
- What is llms.txt?
- llms.txt is a proposed convention (llmstxt.org) for a plain-text file at a site's root that gives AI models and agents a curated, markdown-formatted summary of the site — a title, short summary, and categorized lists of links — since most sites are too large or JavaScript-heavy for an LLM to process in full during a chat session.
- Is my llms.txt content or the URL I check sent anywhere?
- Pasted text is validated entirely in your browser. Checking by URL calls a server endpoint to fetch that page's live content (necessary to avoid cross-origin browser restrictions), which is rate-limited and validates the target isn't a private or internal address before fetching — the fetched text itself isn't stored.
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