The Fedi Links Project: English

The web+ap URI


The web+ap URI scheme is intended to represent web-based ActivityPub objects, as seen in the ActivityPub specification.


Same as https, with the following additional restrictions:

  1. Userinfo is reserved for future use, and unless otherwise specified, MUST be ignored.

See RFC9110, Section 4.2.2 for https.

Encoding considerations

Same as https.

Interoperability considerations

Currently, none of the ActivityPub implementations parse web+ap URIs. There is an open redirector that parses web+ap URIs and turns them into the correct https URI, on a best-effort basis.

It is worth noting that browsers parse these using the WHATWG URL spec, especially when used as e.g. a web-based protocol handler.

This specification was explicitly designed with Browsing Behavior of web+ Links, by the Fedi Links Project in mind.

Functional description

A web+ap URI is an https URI with additional semantics. ActivityPub software supporting this URI MUST treat it as an https URI and then follow the ActivityPub specification, especially when it comes to the exchanged content types (the Accept and Content-Type header).

It is also encouraged for operating systems to provide a fallback mechanism for these URIs. This SHOULD be done in a way that the target website can reject non-ActivityPub objects (like invite links). This fallback mechanism SHOULD be used when no appropriate ActivityPub software is available.

Security considerations

The security considerations are basically the same as https, with additional considerations for this being a valid scheme for registering a web-based protocol handler. The purpose of this URI is to explicitly allow registering a web-based protocol handler, particularly one of the user’s choice, for interacting with the ActivityPub network. More specifically, this would allow the user to use their own e.g. Mastodon instance to interact with ActivityPub URIs, automatically.

No further security considerations are currently known.