Twitter Inc (TWTR.N) said Tuesday it will begin testing ads on its disappearing posts feature called Fleets, as it works to offer more options for advertisers. The social media company previously said it set a goal of doubling its annual revenue by 2023 from last year"s levels, which it plans to achieve in part by selling ads on more parts of its site and mobile app. Fleet ads will be the first on Twitter that appear full screen on phones, the company said. Advertisers generally like full-screen ads because they capture the user"s attention. The new offering is part of Twitter"s aim to catch up to larger social media platforms like Facebook Inc (FB.O) and Snap Inc (SNAP.N), which have long offered a "Stories" posts feature that disappears after 24 hours and is monetized with ads. Brands that create Fleet ads can also use a feature that would direct a user to the company"s website or other web destination if they swipe up on the ad.