llms.txt validator

Validator

Enter a domain (we fetch its /llms.txt) or a full file URL. The fetch runs through our edge function, so CORS restrictions on the target site do not apply.

Paste file content

What we check

The validator implements the rules from llmstxt.org:

• H1 required. Exactly one level-1 heading, first non-empty line.
• Blockquote summary. Recommended right after the H1.
• H2 file-list sections. Each section is a Markdown list of - [name](url) items, with optional : notes.
• Absolute URLs. Relative URLs are flagged as warnings.
• No content outside sections. After the first H2, only file lists are expected.
• Size guard. Files larger than 50 KB get an info-level note suggesting llms-full.txt.

Each diagnostic includes a rule code (e.g. H1_REQUIRED, URL_RELATIVE) so you can grep for it in CI logs.

Use it from CI

The same parser that powers this page can be wired into your build: the rule codes below are stable, so a script can grep them in CI logs. A minimal Node check:

import { readFileSync } from 'node:fs';
import { parseLlmsTxt, summarize } from './validator/validate'; // same parser as this validator

const input = readFileSync('public/llms.txt', 'utf8');
const parsed = parseLlmsTxt(input);
const sum = summarize(parsed);

if (!sum.passes) {
  for (const d of parsed.diagnostics) {
    console.error(`${d.severity.toUpperCase()} [${d.rule}] line ${d.line}: ${d.message}`);
  }
  process.exit(1);
}
console.log(`OK, ${parsed.sections.length} sections, ${parsed.sizeBytes} bytes`);