MuseScore is the world's leading free and open-source software for writing music, with a user-friendly interface and immensely powerful features. It is free to install on Windows, Mac, and Linux. MuseScore is the software used to create the scores found on musescore.com.
MuseScore.org/ is the software’s official website, where you can download MuseScore for free, search the MuseScore Handbook, communicate with developers (and get involved in the open-source development yourself!), donate to the project, and get help from the community in the forums.
The MuseScore notation software is used to create your own scores or edit ones you find online. But you can view, print, and play scores on musescore.com directly in your browser, with no other software or special plugins required.
The musescore.com website is a sheet music-sharing social platform. Anybody can create a free account and upload their sheet music, to share with the world or to be kept as a private backup. A PRO account is available to unlock more features of the site, but musescore.com will always offer a free account.
MuseScore apps for iOS and Android connect to your musescore.com account and allow you to search for music, play, transpose, and view individual parts of a score.