Jesar Shah, product manager at Twitter:
Today, we’re introducing Bookmarks, an easy way to save Tweets for quick access later. But wait, there’s more! Today’s update makes sharing better, too. With our new “share” icon on every Tweet, you’ll be able to bookmark a Tweet, share via Direct Message, or share off of Twitter any number of ways. Because we put all sharing actions together in one place, it’s easier to save and share privately or publicly — in the moment, or later.
This looks great. Bookmarking is easily one-third to one-half of how I use the “like” button. A key difference between the two is that bookmarks are private; likes are public and, for a few years now, followed users’ likes have been inserted at the top of the algorithmic timeline. If Twitter were driven less by juicing “engagement” metrics, this feature might not be necessary.
Unfortunately, there’s nothing in this announcement nor anything in Twitter’s documentation that suggests they’re making this available to third-party developers; I hope they do.