Well-known URI
A well-known URI is a resource published at a path beginning /.well-known/ on a host, under the registry RFC 8615 establishes for exactly this purpose: letting a new protocol or specification define a standard, discoverable location for site-wide metadata without inventing a new DNS record type or coordinating with whatever content the host already serves. A specification that needs this kind of discovery registers its own suffix after /.well-known/ with IANA rather than picking an arbitrary path that might collide with something else already on the host; examples already in wide use include /.well-known/acme-challenge/ for ACME domain-control validation, /.well-known/security.txt for a site's security contact per RFC 9116, and /.well-known/oauth-authorization-server for OAuth 2.0 Authorization Server Metadata. RFC 8615 obsoletes the earlier RFC 5785, which introduced the same convention with a narrower registration process. Despite the shared "well-known" name, this is a completely different registry from a well-known port: a well-known URI is a path on a specific host's web server, registered in IANA's Well-Known URIs registry, while a well-known port is a TCP/UDP port number reserved in IANA's separate Service Name and Transport Protocol Port Number Registry under RFC 6335 -- the two namespaces don't interact, and a protocol can use either, both, or neither.
By AdminKit team, Netbase JSC · Updated