Syncthing

Syncthing is an open-source, continuous file synchronization program that synchronizes files between two or more computers in real time. Unlike Dropbox or Google Drive, Syncthing transfers data directly between your devices using a peer-to-peer protocol — no data ever passes through or is stored on a central cloud server.

Syncthing works across Windows, macOS, Linux, Android, and other platforms. It features conflict resolution, selective sync, per-folder ignoring rules, and encrypted node connections using TLS. An optional relay infrastructure helps when devices cannot connect directly (e.g., both behind NAT), but communication is always encrypted end-to-end.

Because there is no central server, there is no subscription, no storage limit (except your own devices), and no company with access to your files. Syncthing is particularly popular among privacy-conscious users and self-hosters who want cloud-like convenience without the cloud.