IETF RFC 5785
Defining Well-Known Uniform Resource Identifiers (URIs)
|Publication Date:||1 April 2010|
It is increasingly common for Web-based protocols to require the
discovery of policy or other information about a host ("site-wide
metadata") before making a request. For example, the Robots
Exclusion Protocol specifies a way for automated processes to
obtain permission to access resources; likewise, the Platform for
Privacy Preferences [W3C.REC-P3P-2002041
While there are several ways to access per-resource metadata (e.g., HTTP headers, WebDAV's PROPFIND [RFC4918]), the perceived overhead (either in terms of client-perceived latency and/or deployment difficulties) associated with them often precludes their use in these scenarios.
When this happens, it is common to designate a "well-known location" for such data, so that it can be easily located. However, this approach has the drawback of risking collisions, both with other such designated "well-known locations" and with pre-existing resources.
To address this, this memo defines a path prefix in HTTP(S) URIs for these "well-known locations", "/.well-known/". Future specifications that need to define a resource for such site-wide metadata can register their use to avoid collisions and minimise impingement upon sites' URI space.