llms.txt vs. robots.txt: What's the Difference?
robots.txt blocks crawlers; llms.txt describes your site for AI systems. Here's exactly how the two files differ, and why you likely need both.
Both files live at your site's root and both are read by automated systems, which is where the similarity ends. llms.txt and robots.txt solve opposite problems for different audiences, and neither one substitutes for the other.
What robots.txt Does
robots.txt is a decades-old, formally standardized convention that tells search engine crawlers which parts of your site they may or may not access. It's a permissions file: a list of allow and disallow rules per user-agent. It says nothing about what your site contains or means — only where a crawler is and isn't allowed to go.
What llms.txt Does
llms.txt is a community-proposed convention, not a formal standard, that does the opposite job: it proactively describes what your site contains, in a structured, AI-readable summary. Instead of telling an AI system where it can't go, it hands over a curated overview of your site name, purpose, and key pages so the system doesn't have to parse your full HTML — navigation, scripts, and all — to figure out what you offer.
| robots.txt | llms.txt | |
|---|---|---|
| Purpose | Access control | Content summary |
| Audience | Search engine crawlers | AI systems and chatbots |
| Standard | Formally established | Community-proposed convention |
| Format | User-agent / Allow / Disallow rules | Markdown summary and page list |
| Affects search rankings? | Yes — controls crawl access | No — not a Google ranking factor |
Do You Need Both?
Yes, and they don't conflict. robots.txt continues to control what traditional search crawlers can index; llms.txt is an additional, separate file that gives AI systems a head start on understanding your site rather than forcing them to crawl and parse every page. Publishing one is not a substitute for the other — most sites should maintain both.
Common Mistake: Treating Them as Interchangeable
Because both files sit at the domain root and both are read by automated systems, it's easy to assume editing one covers the other's job. It doesn't — a disallow rule in robots.txt has no effect on what an AI system reads from llms.txt, and listing a page in llms.txt has no effect on whether a search crawler is allowed to index it. Keep them conceptually and operationally separate.
Use the LLMs.txt Generatorto crawl your site and produce a correctly formatted llms.txt file in seconds — it doesn't touch or read your existing robots.txt, since the two are unrelated inputs to unrelated systems.