llms.txt is a plain text file, written in simple Markdown, that you place at yourdomain.com/llms.txt. It's a short, clean summary of who you are and what your key pages contain, written specifically so an AI model can read it without wading through navigation menus, cookie banners, and JavaScript your website's human visitors never notice.

Open ChatGPT, Perplexity, Claude and Gemini. Ask each one the question your best customer would ask about your category and then read what comes back. That's the test, and it costs nothing but ten minutes. Most organisations skip this step entirely. They jump straight to schema markup or an llms.txt file without ever checking whether they show up at all, and importantly, not knowing who's showing up in their place.

Search engine optimisation is no longer the whole game. In 2026, more of your prospective clients are asking ChatGPT, Perplexity, Claude or Gemini a question and acting on the answer they're given, without ever clicking through to a website. If your content isn't structured to be understood, extracted, and trusted by those systems, you could rank #1 on Google and still be invisible to the potential clients who need you. The shift from SEO to AIO is changing what "being found" even means.