Who speaks MCP.

What counts as adoption. A domain appears below only when the file parses as JSON and carries the two things a descriptor exists to carry: a name, and an absolute https endpoint. A 404, a timeout, or a page of HTML served for every unknown path is not adoption. Nor is JSON that is not a descriptor: github.com answers this exact path with {"error":"Not Found"}, and a check that only looked for a 200 would have published GitHub as an adopter.

A descriptor is a claim the domain makes about itself, not proof that a working MCP server answers there. We fetch a static file. We do not open a session, we do not call initialize, and we do not check that anything is alive at the endpoint it names.

Why there is no percentage on this page. We have asked only a fraction of the catalog so far, and the domains we asked were not sampled at random. Dividing the number above by the whole catalog would measure the sample and print it as the internet. A domain nobody has asked is not a domain without MCP.

An answer is not an advertisement. A domain appears below only when the TXT record at that name is an MCP advertisement, carrying v=mcp… or naming an endpoint. A domain with wildcard DNS answers every possible name, so an answer on its own proves nothing. The detection validates the record itself.

A small number here is a real reading, not a broken page. It counts one narrow thing: a record almost nobody publishes, because nothing reads it. Each row is the domain's most recent reading, so the set updates on the scan cadence, not in real time.