Tumblr will add support for ActivityPub – an open decentralized protocol of social networks, which today underlies such social networks as the Twitter alternative Mastodon, the Instagram-like Pixelfed, the video streaming service PeerTube and others.

The news became known in response to a Twitter user’s complaint about the difficulties in the work of Mastodon. Automattic CEO Matt Mullenweg, whose company acquired Tumblr from Verizon in 2019, suggested to the user go to Tumblr as the site will soon “add activitypub for interconnect”.

This means that Tumblr will transform from a niche blogging platform to part of a larger, decentralized social network, its user base has grown in recent days as people are leaving Elon Musk’s Twitter in search of new communities.

The ActivityPub protocol, as explained on its site, provides a client-to-server API for creating, updating, and deleting content, as well as a federated server API for delivery messages and content subscriptions.

In practice, this means that Mastodon users can interact with and follow users of other instances (regardless of running nodes) and other social applications (such as PeerTube) that also support the ActivityPub implementation. This creates a social network chain where users can find and follow each other without having to create new accounts on each new service.

This is an alternative approach to today’s social media, where a post on one platform cannot be viewed by users on other platforms unless you upload or repost the content directly or share a link to another site where that content can be found.

If Tumblr adds ActivityPub support, it will mean that Mastodon users will be able to follow Tumblr users’ posts from their own Mastodon instances, without having to use the Tumblr app. It could also provide Tumblr users with an entry point into the so-called fediverse without having to deal with some complications associated with the first registration on Mastodon.

Tumblr has already benefited from the outflow of Twitter followers, increasing the number of installed applications in the US by 7% compared to the week before the acquisition and 7 days after it, according to data.ai. According to Sensor Tower’s data, 12 days after Twitter’s acquisition, Tumblr’s worldwide downloads increased 77% to 301,000 compared to 170,000 12 days before acquisition.

Matt Mullenweg later offered a look at Tumblr’s metrics, noting at interview to The Atlantic that downloads of the Tumblr app for iOS increased by 62% in the week after Musk took over Twitter.

And even before Musk took over Twitter, Mullenweg was thinking about how Tumblr could better compete with Twitter in the future.

Automattic already has some experience with ActivityPub.

In addition to Tumblr, Automattic operates the WordPress.com blogging service and contributes to the WordPress open-source blogging software platform. The latter today offers the ActivityPub plugin for WordPress sites self-hosting. It allows WordPress blog readers to follow their posts on Mastodon and other integrated social platforms.