Licensed music in video games has also affected video game streaming, such as Let's Play videos. Due to the Digital Millennium Copyright Act (DMCA), most popular video sharing and streaming site implement automatic forms of detecting copyrighted music from most music labels, and flag or block user videos that employ that music, such as YouTube's ContentID system. These actions apply equally to videos of people playing video games, flagging the video from the licensed music in the game. To avoid this, games using licensed music may offer a "stream-safe" music option, either disabling the music playback or replacing the licensed music with copyright-free or royalty-free music.