Dropbox is described as 'Worlds leading online storage and file sync service. You get 2GB free. Apps for all major platforms' and is one of the leading apps in the Backup & Sync category. There are more than 100 alternatives to Dropbox for a variety of platforms, including the Web, Windows, Mac, Android and iPhone. The best alternative is Nextcloud, which is both free and Open Source. Other great apps like Dropbox are Google Drive (Freemium), ownCloud (Freemium, Open Source), MEGA (Freemium) and Syncthing (Free, Open Source).