Twitter has listed a new paid-for “Twitter Blue” service on app stores, suggesting the social media company may launch its long-rumoured subscription service soon. Mobile phone app stores showed the service, although its expected features did not yet appear to be available. A subscription plan has long been expected as Twitter looks for more ways to make money from its large user base. In April, the company said it had 199 million users from whom it could make money every day, a 20% year-on-year increase. On Apple’s App Store Twitter lists “Twitter Blue” under in-app purchases for £2.49 in the UK and $2.99 in the US store. On the Android store the Twitter listing shows “in-app purchases” but does not list pricing for the service. Expected features for the paid service include an “undo” button to allow users to recall tweets for a few seconds after sending them, a “collections” feature so users can make separate lists of tweets (rather than relying on a single bookmarks list), and a mode to make it easier to read long threads. The app listings for Twitter Blue were discovered by Jane Manchun Wong, an independent researcher who works on unearthing app features before they are released. On Thursday, she said the service included new colour themes and icons. Charging users for extra features could significantly increase Twitter’s money-making abilities. In the first three months of 2021 alone, the company made revenues of $1bn (£700m). Finding other sources of revenue could also make it less susceptible to fluctuations in global demand for advertising, as well as technological changes such as Apple’s clampdown on tracking on its devices. Twitter, which is run by its founder, Jack Dorsey, has bought companies in the subscription economy. These included the January purchase of Revue, which offers paid-for email newsletters, and Scroll, a service that removes advertisements from news websites. Earlier this month, Twitter introduced a “tip jar” feature, allowing users to make small payments to others via third-party services. The feature is initially limited to a small number of users.