Tumblr to add support for ActivityPub, the social protocol powering Mastodon

As I understand it, this is quite significant. This paragraph in particular pretty much sums it up: "If Tumblr were to add ActivityPub support, it means users on Mastodon could follow Tumblr users’ posts from their own Mastodon instance — 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 face some of the complexities that are involved with signing up for Mastodon for the first time."