llms.txt Checker: Does Your File Exist, Is It Valid, Can AI Bots Read It?
llms.txt is a new standard that hands AI assistants like ChatGPT, Claude and Perplexity a content map of your site in a single file. Index Harmony checks in seconds whether your file exists, follows the llmstxt.org format, and whether the links inside it actually work.
No sign-up · 30–90 seconds · 100+ checks
What is llms.txt?
llms.txt is a small markdown file that lives at the root of your site. Per the llmstxt.org standard it has three parts: an H1 heading with the site name, a short summary describing the site in a sentence or two, and link lists that group your most important pages.
Its purpose is simple: instead of HTML, menus and script noise, it gives AI assistants a readable content map of your site at a glance. An AI tool gets the answer to "what is on this site, and which page should I read?" in a single request.
The standard's companion file, llms-full.txt, goes further: rather than a map, it serves your entire content as one markdown file — so tools with large context windows can read everything in one pass.
What do we check?
File presence
Does /llms.txt return 200, and is it served with the right content type (plain text / markdown)?
Format validity
Is the llmstxt.org structure in place: an H1 title, a short summary and sectioned link lists?
Link health
Does a sample of the links listed in the file actually return 200? Broken links send AI assistants into dead ends.
Freshness signal
Does the file reflect your site as it is today, or is it a forgotten stale copy?
llms-full.txt presence
Do you have the full-content version? If so, its accessibility and content type are reported too.
Who is it for?
Docs and SaaS sites
The llms.txt standard grew out of developer documentation; map your API and product docs for AI tools.
Publishers
Help AI assistants land on the right article when answering questions; keep key content at the top of the map.
E-commerce sites
Put category and guide pages on the map so AI shopping assistants grasp your product structure faster.
Agencies and SEO pros
Audit the presence and quality of llms.txt across client sites in one scan, and document it in a report.
Frequently asked questions
What is llms.txt?
A markdown file at your site root (/llms.txt). Per the llmstxt.org standard it consists of an H1 heading with the site name, a short summary, and lists grouping links to your key pages. It gives AI assistants a content map of your site in a single request.
How do I create an llms.txt?
Anyone who knows markdown can write one by hand: an H1 site name, a one-paragraph summary and sectioned link lists. On WordPress, the Index Harmony plugin publishes a virtual llms.txt from your site's content in one click — no manual file to keep up to date.
What is llms-full.txt, and how is it different?
llms.txt is a content map (summary plus links); llms-full.txt is the expanded version that serves your entire content as a single markdown file, so AI tools with large context windows can read everything in one request. Our check reports the presence of both files.
Will adding llms.txt get me shown in ChatGPT?
No one can guarantee that; the standard is young and adoption varies by AI provider. llms.txt is a low-cost signal that helps AI bots understand your site and find your key pages — a solid machine-readability step, not a ranking promise.
What exactly does the checker test? Is it free?
Completely free, no sign-up. It checks that the file exists with the right content type, follows the llmstxt.org format (title/summary/link structure), that a sample of listed links returns 200, whether it looks up to date, and whether llms-full.txt exists. The findings appear as part of your 100+ check AI-readiness report.
Check your llms.txt now
Enter your URL — your 100+ check report, llms.txt findings included, is ready within 90 seconds.