The best llms.txt validators, compared by someone who built one
Roundup
Six tools that check an llms.txt, what each one is actually good at, and which to reach for. I maintain one of them, so read the self-interest accordingly — the honest version is that for several of the jobs below, you should use someone else's.
Every tool here was opened and read on 8 October 2026. Prices and features change; re-check before relying on them.
First, the uncomfortable thing
Google has said plainly that Search does not use llms.txt, and no major answer engine documents it as a ranking or citation factor. Sequel's checker says this on its own tool page, which is to their credit. So no validator here can raise your rankings, and any that implies otherwise is selling something.
What a valid file does buy you is narrower and real: when an agent or an assistant does fetch it, it finds a clean map instead of a broken one. That is worth ten minutes. It is not worth a subscription to a tool that promises traffic.
The six
1. Sequel's llms.txt checker — the most honest quick check
sequel.sh verifies the mechanics: that the file exists, returns HTTP 200 as plain text, has not been silently rewritten into an HTML page by your framework or CDN, and how many pages it links to. That HTML-rewrite check is a real failure mode, and reading their page is what made me go back and score it properly in mine — it used to be filed as a mild note about an unusual content type rather than the delivery failure it is.
It also refuses to inflate a score for merely having the file. If you want one quick, unsentimental read on whether your file works, start here. It is part of a broader GEO audit suite, so there is a product behind it, but the checker itself is free and open.
2. llmvalidator.io — the one that handles all three file types
llmvalidator.io validates llms.txt, llms-ctx.txt and llms-full.txt with rules and size limits per format, and it accepts input three ways: fetch from a URL, paste the content, or upload the file. It also does character-encoding analysis — BOM detection, UTF-8 checks, comparing against the server's headers.
If you work with llms-ctx.txt, or you have a file that is not published yet and exists only on your disk, this is the most direct fit. It has accounts and a pricing page, so check the current terms for whatever you need beyond the free check.
3. llms-txt.io — the one that maintains the file for you
llms-txt.io is really a generation and maintenance service with a validator attached. Paid plans ($15/mo and $49/mo at the time of writing) keep "managed sites" current on a weekly or daily schedule, serve them from a stable URL, fire a change webhook, and build llms-full.txt up to a page budget.
Its free validator describes its link check as "samples your links and flags dead ones." If nobody at your company owns the file and your content moves constantly, this is the only tool on the list that solves that, and it is worth paying for. A longer comparison with this one is here.
4. Chrome Lighthouse — the one you already have
Lighthouse audits sites for an llms.txt as part of its agentic-browsing checks, and the llms.txt specification itself cites this as evidence of adoption. It is already in your browser's DevTools and in most CI setups, with nothing to sign up for.
It is a presence-and-basics check inside a much larger performance audit, not a deep validator. But if you want the file watched by something already in your pipeline, it costs nothing to turn on.
5. llms.txt Hub — better as a directory than as a validator
llmstxthub.com is the best-known directory of sites publishing an llms.txt, which makes it the fastest way to read real files from real companies before writing your own. It also has a validator, but that page asks you to sign in.
Use it for the examples. For the validation itself there are faster options above that do not ask who you are. (Disclosure: this directory lists my tool.)
6. Agency lead-gen checkers — fine, with eyes open
Several SEO agencies publish a free checker: MRS Digital, RankRay, Techqee. They work, and they are free.
They also exist to introduce you to an agency that sells SEO services, and the tool is usually a thin structural check rather than the main product. Nothing wrong with that — just know what the page is for before you read its recommendations as neutral.
And mine: llms.txt Validator
This one fetches every linked URL rather than sampling, which matters because the usual real failure is one dead link in sixty, not a file full of them. It needs no account or API key, including for the JSON API, so it drops into CI with nothing to provision. It follows spec-v2 subpath files — example.com/docs resolves to /docs/llms.txt, walking up to the root only on a definitive 404. And it reports the surrounding agent-readiness signals in the same run, plus it is callable as an MCP tool by an agent.
It also flags the case where a 200 came back as HTML — a catch-all route or CDN rule answering instead of the file — as a structural error rather than a footnote. Credit where due: Sequel surfacing that is what prompted the change.
What it does not do: generate anything, keep any file current, or remember your history. If those are your problem, two of the tools above beat it outright.
Which to use
| If your problem is… | Use |
|---|---|
| "Is my file broken at all?" — fastest honest read | Sequel |
| Dead links inside an otherwise valid file | This one |
Validating llms-ctx.txt, or a file not published yet | llmvalidator.io |
| Nobody owns the file and content keeps moving | llms-txt.io (paid) |
| A check inside a pipeline you already run | Lighthouse |
| Seeing how other companies wrote theirs | llms.txt Hub |
| Checking it in CI with no account | This one's API |
What none of them will do
None of these tools will make an AI assistant cite you. They check a file. Whether that file earns you anything depends on whether the pages it points at are worth reading, which no validator can measure — including mine.