llms.txt vs robots.txt
robots.txt tells crawlers what they're allowed to fetch. llms.txt tells AI models what's worth reading and how to interpret it. They serve different audiences and live next to each other at your domain root.
These two files are often confused but solve opposite problems. robots.txt is permission ('can you fetch this'); llms.txt is curation ('here's what matters'). Both live at the root of your domain. Most sites need both, configured for different audiences.
What they share
Where they differ
| Topic | llms.txt | robots.txt |
|---|---|---|
| Audience | AI models ingesting content | Search and AI crawlers fetching URLs |
| Format | Markdown with H1, summary, links | Directives (Allow / Disallow / User-agent) |
| Purpose | Curate the canonical pages for AI | Permit or block crawler access |
| Granularity | A single curated list per site | Per-user-agent rules |
| Maturity | Emerging standard (2024+) | Established since 1994 |
Publish an llms.txt whenever you want AI models to ingest a curated subset of your site rather than crawling everything. It's especially valuable for documentation, knowledge bases, and product catalogs where signal-to-noise matters.
Configure robots.txt on every site. Use it to explicitly allow AI crawlers (GPTBot, ClaudeBot, PerplexityBot, Google-Extended) and to block known abusive bots. A missing robots.txt is fine; a misconfigured one can de-index your entire site.
A SaaS publishes a robots.txt allowing GPTBot, ClaudeBot, PerplexityBot, and Google-Extended on all paths except /admin. The same site publishes an llms.txt linking to its docs root, API reference, changelog, and security page — telling AI models which 4 sections are worth reading first.
The bottom line
Publish both. robots.txt controls access; llms.txt controls interpretation. Together they're the minimum viable AI-search setup.
See how your site scores on both
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Run free scanFrequently asked questions
Do AI engines actually respect llms.txt today?
Adoption is partial but growing. Major models check for it; the value is forward-compatibility plus immediate signal to any crawler that does honor it.
Can llms.txt block content?
No — that's robots.txt's job. llms.txt only curates and recommends; it doesn't restrict access.
Should the llms.txt link to PDFs?
Prefer HTML — AI engines parse it more reliably. If a PDF is canonical, link to it but also publish an HTML version alongside.
Is llms.txt an official standard?
It's an emerging community standard, not an official W3C spec. Adoption among AI vendors and publishers is what gives it weight — and that adoption has grown sharply since late 2024.