Right now, Twitter Blue subscribers get access to Bookmark Folders, Reader Mode, and an Undo Tweet option. Expect even more premium features as we learn what subscribers want to include in their experience!
Note: If you purchase Twitter Blue on iOS, and log into the same account on Twitter for Android, you may be able to access some features, but we haven’t optimized those experiences yet. We recommend only using Twitter Blue on iOS during the limited release for Canada and Australia.
Undo Tweet gives you the option to retract a Tweet after you have sent it, but before it is visible to others on Twitter. Tapping the undo option sends you back to the Tweet composer where you can make changes before posting the Tweet, or deciding not to post at all.
When you activate this feature, a countdown appears so you know the time left until your 30-second Tweet Undo period expires, and your Tweet appears on Twitter. Shorten or lengthen the expiration window to 5, 10, 20 or 60 seconds under the Twitter Blue feature settings menu, or easily skip it altogether when you select Send now.
-"About Twitter Blue"