llms.txt: The Essential Guide for AI Crawlers & Website Optimization

What llms.txt actually does

robots.txt tells search engine crawlers which pages to index. llms.txt does something similar for AI systems. It's a machine-readable index of your most important content, placed at the root of your domain so AI models can find it automatically.

Why AI needs a different signal

Search engines were built for humans. Google reads your HTML and renders your JavaScript. AI language models skip all that. They process raw text, and the cleaner that text is, the better they understand and cite your content.

Raw HTML is the worst format for AI. A typical blog post weighs in at over 15,000 tokens when parsed from HTML — navigation bars, footers, scripts, and CSS noise included. The same post in clean Markdown? Closer to 2,800 tokens. That's an 80% reduction. Legible's Markdown conversion handles this automatically.

What goes in an llms.txt file?

A well-formed llms.txt file includes:

• A brief description of your site and what it covers
• Links to your main pages and their Markdown equivalents
• Optional: usage permissions (can AI systems summarize this? Train on it?)

The problem with maintaining it by hand

The moment you add a new blog post, your llms.txt is out of date. Nobody wants to maintain another file by hand, and most teams won't. Legible auto-generates and updates your llms.txt whenever your CMS changes, so you don't have to think about it.

Getting started

If you're on Webflow, you can install Legible from the Marketplace and have a live llms.txt in minutes. On another platform? Check our roadmap. WordPress and Drupal support are coming soon. See our setup documentation to get started.

Platform-Specific Setup Guides

Looking for step-by-step instructions for your CMS? These companion guides walk you through setup and compare your options:

• How to Set Up llms.txt on Webflow Without Coding — Manual vs. automated setup, the maintenance problem, and a side-by-side comparison of approaches.
• The Best Automated llms.txt Generators for WordPress — A comprehensive comparison of 12 plugins and platforms, with a recommendation matrix by use case.
• How to Optimize Your Website for AI Crawlers Automatically — The complete technical guide to making your site readable by GPTBot, ClaudeBot, PerplexityBot, and 20+ other AI systems.