The 24-year-old singer teased the announcement last week with a video of herself pushing an elevator button marked "18," a screenshot of a phone set at 5 o'clock and a picture of the Yahoo! logo.
Swift is expected to perform new music and announce the release date of her fifth studio album at the event. The singer last released Red in October 2012, which included the hit singles "We Are Never Ever Getting Back Together," "Begin Again" and "22." The album has sold over 4 million copies in the U.S. since its release.
The live stream will take place in New York City at 5 p.m. ET August 18 on Yahoo!. Swift announced her third studio album, Speak Now, via live stream in 2010, and performed three songs from the new record at the event. The singer will appear on The Tonight Show on August 13, and is scheduled to perform at the 2014 MTV Video Music Awards on August 24.