Twitter is rolling out a change to its official iOS app:
See it? Tweet it! Our updated camera is just a swipe away, so you get the shot fast. Rolling out to all of you over the next few days. pic.twitter.com/moOEFO2nQq— Twitter (@Twitter) March 13, 2019
Swipe left to bring up the camera, take a pic, add captions and location info, then post. Rolling out over the next day or so.
Casey Newton, writing for The Verge, took the new interface for a spin, has more details here.