Twitch took to Twitter to warn its creators of the sudden influx of DMCA takedown requests it's been receiving for clips from various creators using background music, specifically in the timeline of 2017-2019. The DMCA, or the Digital Millennium Copyright Act, is a copyright law for the wide web, put in place to protect copyright owners from infringement online.
In Twitch's statement, creators are advised to remove clips they know feature copyrighted material and Twitch also states that, since many creators have a vast video archive, it's working to make it easier to achieve. Are you interested in learning more about music copyright on Twitch? Read more here.