Methodology

Measurement principles

• Primary source first. Provider documentation and the served public file take precedence over summaries.
• Date every observation. A result describes the checked response at a moment in time, not a permanent property of a domain.
• Separate publication from use. A reachable file shows that it was published. It does not establish automatic discovery, AI traffic, ranking, or answer inclusion.
• Publish the method with the number. The panel, result files and release manifest remain downloadable alongside the pages that summarize them.

Fixed-panel tracker

The tracker tests a curated fixed panel of 219 public hosts. On the snapshot dated 2026-10-05, 217 hosts were testable and 125 returned a qualifying llms.txt response. A host qualifies only when its requested file is public, returns HTTP 200, is not an HTML app shell, and begins with a Markdown H1.

The panel is intentionally developer-heavy. It is useful for comparing this same cohort over time, not for estimating all websites. The full host list and raw metrics are available at /adoption-panel.json and /adoption-stats.json.

V2 discovery checks

A separate snapshot checks observable discovery signals on verified files: linked-page reachability, Markdown alternates, the describedby relation, and path-scoped files. The latest release checked 330 linked pages. It found 40 pages with a Markdown alternate, 9 pages with describedby, and 23 hosts with a qualifying subpath file.

These are implementation observations only. They do not claim that any client consumes a relation automatically. The raw snapshot is available at /v2-adoption-stats.json.

What the data cannot prove

• It cannot show that an AI product read a file, used it in retrieval, or cited it in an answer.
• It cannot establish a Google ranking effect. Google documents that it does not use llms.txt for Search or its generative search features.
• It cannot turn a selected panel into a global adoption estimate.
• It cannot infer a relationship, partnership, customer status or endorsement from a public file.

Downloads and reuse

Public measurement data uses the repository’s MIT license. Refer to each source site for the terms applying to its original files.

Cite the snapshot date and its identifier when reusing a figure. The machine-readable release manifest contains the source hash, scope and limits: JSON, CSV, and status. For wording and commercial-disclosure rules, see the editorial policy.