Free llms.txt Validator
Check your llms.txt file for spec compliance. Paste the content or point us at your site — we'll find missing headings, malformed links, duplicate URLs, and structural issues.
Why Validate llms.txt?
llms.txt is still a young spec, and a silently-malformed file is easy to ship. If your H1 is missing, your link syntax is wrong, or you have duplicate URLs, AI assistants will either misinterpret the file or skip it entirely.
What We Check
- H1 title and blockquote summary presence
- Link syntax, URL validity, and protocol consistency
- Duplicate URLs, empty or overly large sections
Severity Levels
- Errors — the file won't parse correctly and must be fixed
- Warnings — the file parses but has quality issues worth fixing
- Info — optional improvements that tighten the file
Frequently Asked Questions
It parses your llms.txt per the spec at llmstxt.org and reports: missing H1 title (error), missing blockquote summary (info), malformed link syntax (error), invalid or non-http(s) URLs (error), duplicate URLs across sections (warning), empty sections (warning), overly large sections that exceed ~15 links (warning), and mixed http/https protocols (info).
Yes — use Paste mode. You can draft your llms.txt locally, paste it into the validator, iterate on the structure, and only publish once it's clean. Paste mode has a 256 KB input limit which is well beyond any realistic llms.txt file.
We fetch https://yourdomain.com/llms.txt directly — no setup required. If the file isn't found we return a clear 404 message. This is the right mode for auditing a site you're responsible for (or a competitor's) without copying the content manually.
Errors mean the file won't parse correctly and must be fixed — for example a missing H1 or a malformed link. Warnings mean the file parses but has quality issues that hurt how LLMs consume it — duplicate URLs, empty sections, sections with too many links. Info issues are optional improvements that tighten the file without being strictly necessary.
Yes. No sign-up, no credit card. The anonymous path validates any number of files. GeoVector's paid plans add continuous monitoring — we re-validate your llms.txt on a schedule and alert you when something drifts, which matters most on sites with frequent content changes.
Every rule this validator applies
Errors are things a parser cannot recover from. Warnings parse fine but will read badly to a model. Info items are judgement calls.
| Severity | Code | When it fires |
|---|---|---|
| Error | missing_h1 | The file does not start with a single "# Site name" heading. |
| Error | malformed_url | A link target does not parse as a URL. Relative paths land here. |
| Error | unsupported_protocol | A link uses something other than http:// or https://. |
| Error | missing_link_title | A list item has a URL but no link text. |
| Warning | no_sections | No "## Section" headings, so every link sits in one undifferentiated pile. |
| Warning | empty_section | A heading with no links under it. |
| Warning | large_section | More than 15 links in one section. Split it so the file stays scannable. |
| Warning | duplicate_url | The same URL appears twice; the report names both line numbers. |
| Info | missing_summary | No "> summary" blockquote under the title. |
| Info | no_optional_section | No "## Optional" section, so nothing is marked as safe to skip. |
| Info | mixed_protocol | The file mixes http:// and https:// links. |
Nothing here is enforced by a specification body — llms.txt is a proposal, and these rules encode the shape it describes plus what breaks in practice when a file is consumed by a model with a limited context window.
A file that passes, and one that does not
Compare the two before you write your own.
# Example Analytics
> Product analytics for teams that ship weekly.
## Docs
- [Quickstart](https://example.com/docs/quickstart): Install the SDK and send a first event.
- [Event API](https://example.com/docs/api/events): Endpoint reference and payload limits.
## Optional
- [Changelog](https://example.com/changelog)## Docs
- [Quickstart](/docs/quickstart)
- (https://example.com/docs/api/events)
- [Quickstart](https://example.com/docs/quickstart)
## Guides
No H1 (error), a relative path instead of a URL (error), a link with no title text (error), a duplicate URL (warning), and an empty Guides section (warning). Every one of them is invisible until something tries to parse the file.
Sources and specifications
Everything on this page is checked against the primary documentation below. If a vendor changes a rule, that is where it shows up first.
- The /llms.txt file proposal — llmstxt.org
- RFC 9309: Robots Exclusion Protocol — IETF
Last reviewed . We re-check this page against the source specifications whenever a vendor updates one.