Question
Do I need an llms.txt file to appear in AI answers?
Short answer
Not for Google, which states in writing that no new file, markup or schema is needed. No assistant maker has published that it reads llms.txt.
Google's documentation is unusually direct on this. To appear in AI Overviews or AI Mode a page must be indexed and eligible to show with a snippet, and there are, in its words, no additional technical requirements. It then says explicitly that you do not need to create machine-readable files, AI text files, or special schema.org markup.
That sentence is worth reading twice, because a large part of what is sold as generative engine optimisation proposes exactly those artefacts. The honest position today is that llms.txt is a proposal with no published adoption by any major assistant: no crawler documentation from OpenAI, Anthropic, Google or Perplexity mentions reading it.
This site publishes an llms.txt and a Markdown twin of every page, which deserves the same scepticism. We do it because it costs little and because the content exists anyway, not because anyone has demonstrated that a model reads it. If that changes, it will be because someone publishes a measurement, and the measurement will go in this dataset.
What does have published support is duller: be indexed, be current, be specific, and be correctly described by the third-party sources that already get cited. The Tokyo citation audit suggests that last one carries more weight than anything on your own domain for transactional questions.