robots.txt vs llms.txt: What's the difference and why it matters

robots.txt vs llms.txt: what's the difference and which do you need? Your website talks to two audiences now: search engine crawlers and large language models. They want different things, they read content differently, and the files that serve them have almost nothing in common. Most developers know robots.txt. Fewer know llms.txt. Almost nobody understands why you need both. robots.txt: the bouncer robots.txt has been around since 1994. Martijn Koster, a Dutch engineer, proposed it after web crawlers kept hammering his server. The idea was simple: put a text file at your site root that tells bots which pages they can and can't visit. For 28 years it existed as an informal standard. Everyone followed it, nobody had formally ratified it. The IETF finally published RFC 9309 in September 2022, making it official. A typical robots.txt in 2025 looks like this: User-agent: Googlebot Allow: / User-agent: GPTBot Disallow: / User-agent: ClaudeBot Disallow: / User-agent: Google-Extended Disallow