New Delhi: As millions of Twitter user demand an Edit button to correct spelling errors in their tweets, Twitter has started testing an undo tweet feature which could first be rolled out to paid customers via a subscription service. Twitter confirmed to CNET that it is testing the 'undo tweet' feature. App researcher Jane Manchun Wong first discovered a subscription screen tied to the feature. "Twitter is working on app subscription for paid features like 'Undo Tweet," she said in a tweet along with a screenshot on Friday. The feature is different from deleting a tweet which its available to all users at the moment, as undoing a tweet will eventually stop it from being sent. Gmail offers a similar option for emails, where it provides a short window to stop messages from being sent after clicking the "Send" button. The Twitter "undo button" also doubles as a progress bar, showing how long you have to undo a tweet before it gets sent. The `Undo Send` button is likely to provide a 30-second window for users to recall or withdraw a tweet with typos and other errors before anyone can see it. This will, however, be only an alternative to 'Edit' button users have been demanding for years. Twitter aims to more than double its total annual revenue to over $7.5 billion in 2023 with at least 315 million mDAU (monetisable daily active users), its CEO Jack Dorsey has said, and a paid subscription service is another move to achieve the goal.