AI Preferences (IETF aipref)

AI Preferences, usually shortened to aipref, is an IETF standards effort that gives publishers one shared vocabulary for saying how their content may be used by AI systems, such as whether it may train a generative model, and defines how to attach those preferences to content through robots.txt or an HTTP header. As of October 2026 it is still a set of Internet-Drafts, not a finished standard.

The IETF chartered the AI Preferences Working Group in January 2025, chaired by Mark Nottingham and Suresh Krishnan. In its announcement, the IETF said AI vendors 'use a confusing array of non-standard signals in the robots.txt file' and that publishers were losing confidence their preferences would be followed. Today each AI company publishes its own tokens, such as Google-Extended or ClaudeBot, and a site has to name every one. aipref aims to replace that with statements about uses rather than about bots.

The work has two documents. The vocabulary draft (draft-ietf-aipref-vocab-08, September 13, 2026) defines three categories of use, each with a short label:

• train-ai: using an asset to modify the learned parameters of a generative AI model.
• ai-use: using an asset as input to a generative AI model when the user did not supply it directly, which covers grounding and retrieval for AI answers.
• search: using an asset in an application whose main purpose is to point users to its location, with links and short excerpts. The draft says this category does not include generating summaries, and that it overrides the other two.

Each category can be set to y (allow) or n (disallow). A category left out is 'unknown', and the draft takes no position on what default a crawler should assume. When several statements conflict, the most restrictive one wins.

The attachment draft (draft-ietf-aipref-attach-05, August 18, 2026, edited by Gary Illyes of Google and Martin Thomson of Mozilla) adds a Content-Usage rule to robots.txt and a Content-Usage HTTP response header. A robots.txt group can say Allow: / and Content-Usage: train-ai=n, and a rule can be scoped to a path, for example Content-Usage: /ai-ok/ train-ai=y. This separates acquisition (Allow and Disallow decide what may be fetched) from usage (Content-Usage says what may be done with it).

The drafts are not done. The working group's charter set August 2026 as the date to send both documents to the IESG, and in mid-October 2026 neither had been sent. The vocabulary draft itself warns that its core sections 'do not yet have consensus', so labels and definitions may still change. Adoption is minimal: a ProxyPicker scan on October 8, 2026 of 6,735 robots.txt files from Chrome's 10,000 most visited origins found 13 using Content-Usage, 12 of them Vinted country sites. The same scan found 122 files with Cloudflare's Content-Signal line and 950 blocking GPTBot by name.

aipref sits next to several related signals. Cloudflare's content signals, launched in September 2025, express a similar idea with different labels (search, ai-input, ai-train). The EU's TDM rights reservation gives opt-outs legal weight in Europe, and the vocabulary draft is written to work both where preferences carry legal obligations and where they do not. Licensing schemes such as Really Simple Licensing go further and attach payment terms. None of these are technical blocks: the draft states plainly that a recipient decides whether to follow a preference.

For AI visibility, the category that matters most is ai-use. Under the draft's definitions, AI-generated search answers fall under AI use rather than search, so a site that sets ai-use=n is asking AI search engines not to ground answers on its pages, which would mean no citations from systems that honor it. A brand that only objects to AI training data collection should set train-ai=n and leave ai-use and search alone. Adding a Content-Usage line costs little, but per-crawler robots.txt rules remain the mechanism AI companies document and follow today.