Free, open-source alternatives to Dropbox

Dropbox stores files in its own cloud and keeps a Dropbox folder on each of your computers in sync with it, so a change saved on one device shows up on the others. It also shares files and folders with other people and keeps earlier versions for a limited time.

The open-source apps below do the same syncing job, but none of them comes with storage of its own: you need your own server or your own devices. Nextcloud Desktop and Seafile sync chosen folders with a Nextcloud or Seafile server that you run yourself or that a provider or your organisation hosts, and both servers add sharing and web access. Syncthing for macOS has no central server at all and copies folders directly between your own devices, so changes only travel while at least two of them are online.