Briar Desktop (beta available) is a messenger for people who need safe, robust communication without a central server. Encrypted messages synchronise directly between devices. When the internet is down, Briar can sync over Bluetooth, Wi-Fi, or removable media; when online it can use the Tor network — reducing exposure to server-side metadata and outages that silence centralized apps.
Related NGI work extends Briar beyond Android so the same peer-to-peer model reaches desktop users.
Project page (NLnet): Briar beyond Android.