Activity Streams extensions

From W3C Wiki

This page documents known AS2 extensions and best practices for using other namespaces in AS2.

More info:

Accepted extensions

Extensions added by ActivityPub

ActivityPub defines some extensions which are included in the default ActivityStreams vocabulary and context.

TODO: Enumerate them here. In the meantime, go see ActivityPub.

as:alsoKnownAs property

Decentralized Identifiers (DIDs) (DID Core v1.0 Terms) defines a alsoKnownAs term, for use as a property of DID documents. SocialCG allowed this term to be defined in the ActivityStreams 2.0 namespace, with the idea that the SocialCG and the DID community may further iterate on the definition[1]. The DIDs specification describes an example of using the alsoKnownAs property for assigning DIDs to web resources.

Proposed extensions

These extensions have not yet been approved by the W3C Social Web Incubator Community Group but are up for review.

as:Hashtag type


The Hashag is an object type, subclass of Object, which is used for hashtag-style tags under the tag property.

as:sensitive property


The sensitive property (a boolean) on an object indicates that some users may wish to apply discretion about viewing its content, whether due to nudity, violence, or any other likely aspects that viewers may be sensitive to. This is comparable to what is popularly called "NSFW" (Not Safe For Work) or "trigger warning" in some systems. Implementations may choose to hide content flagged with this property by default, exposed at user discretion.


Proposed documentation: When *true*, conveys that for this actor, follow requests are not usually automatically approved, but instead are examined by a person who may accept or reject the request, at some time in the future. Setting of FALSE conveys no information and may be ignored. This information is typically used to affect display of accounts, such as showing an account as private or locked.

History: irc discussion about the need for conveying 'locked' in Mastodon