Synology C2 is described as 'Synchronizes data across all your devices, such as computers, mobile devices, or other Synology NAS. Build a private cloud and ensure files are readily available when and where you need them' and is an app in the backup & sync category. There are more than 100 alternatives to Synology C2 for a variety of platforms, including Windows, Web-based, Mac, iPhone and Android apps. The best Synology C2 alternative is Nextcloud, which is both free and Open Source. Other great apps like Synology C2 are Dropbox, Syncthing, Google Drive and MEGA.