Twitter are working on a paid subscription service codenamed Twitter Blue, according to app researcher Jane Manchun Wong, who reverse-engineers popular apps to see what future features are being worked on by developers.

Wong revealed the Twitter Blue service will cost $US2.99 ($4) per month, and allow users to ‘undo’ their tweets, and create collections of bookmarks. Wong says the company is working on a multi-tier system, with higher levels enjoying an uncluttered feed more akin to a news service.