A well-known URI is a

Uniform Resource Identifier A Uniform Resource Identifier (URI), formerly Universal Resource Identifier, is a unique sequence of characters that identifies an abstract or physical resource, such as resources on a webpage, mail address, phone number, books, real-world obje ...

for

URL A uniform resource locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identi ...

path prefixes that start with /.well-known/. They are implemented in webservers so that requests to the servers for well-known services or information are available at URLs consistent well-known locations across servers.

Description

Well-known URIs are

s defined by the

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet standard, Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster ...

in RFC 8615. They are

path prefixes that start with /.well-known/. This implementation is in response to the common expectation for web-based protocols to require certain services or information be available at URLs consistent across servers, regardless of the way URL paths are organized on a particular host. The URIs are implemented in webservers so that requests to the servers for well-known services or information are available at URLs consistently in well-known locations across servers. The

has defined a simple way for

web server A web server is computer software and underlying Computer hardware, hardware that accepts requests via Hypertext Transfer Protocol, HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, co ...

s to hold metadata that any

user agent On the Web, a user agent is a software agent responsible for retrieving and facilitating end-user interaction with Web content. This includes all web browsers, such as Google Chrome and Safari A safari (; originally ) is an overland jour ...

(e.g.,

web browser A web browser, often shortened to browser, is an application for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's scr ...

) can request. The metadata is useful for various tasks, including directing a web user to use a

mobile app A mobile application or app is a computer program or software application designed to run on a mobile device such as a smartphone, phone, tablet computer, tablet, or smartwatch, watch. Mobile applications often stand in contrast to desktop appli ...

instead of the website or indicating the different ways that the site can be secured. The well-known locations are used by web servers to share metadata with user agents; sometimes these are files and sometimes these are requests for information from the web server software itself. The way to declare the different metadata requests that can be provided is standardized by the IETF so that other developers know how to find and use this information.

Use

The path well-known URI begins with the characters /.well-known/, and whose scheme is "HTTP", "HTTPS", or another scheme that has explicitly been specified to use well-known URIs. As an example, if an application hosts the service "example", the corresponding well-known URIs on https://www.example.com/ would start with https://www.example.com/.well-known/example. Information shared by a web site as a well-known service is expected to meet a specific standard. Specifications that need to define a resource for such site-wide metadata can register their use with the

Internet Assigned Numbers Authority The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, Autonomous system (Internet), autonomous system number allocation, DNS root zone, root zone management in the Domain Name Syste ...

(IANA) to avoid collisions and minimize impingement upon sites' URI space.

List of well-known URIs

The list below describes known standards for .well-known services that a web server can implement.

References

Footnotes

{{Reflist Well-known services Well-known URI scheme Hypertext Transfer Protocol Request for Comments