Project Website: https://www.signal.org/

Signal Messenger is a private, encrypted communications app for Android, IOS, Windows, Mac, and Linux. It's strengths are ease of use, functionality, and performance. However, it relies on centralized servers, and requires a smart phone to activate an account. Signal Messenger supports file sharing, group voice and video chats, group IM chats, and automatic contact discovery by scanning your contacts (if you allow it).

Signal must first be installed on a phone to set it up. Download the app from the app store on your device, or for Android, install the APK file from the Signal website.

After installing the app, open it, and grant the necessary permissions. Signal will send a text to your mobile number to confirm it, then activate your account. Set a screen name, and picture, if desired. For ease of use, allow Signal to access your contacts: the app will automatically add Signal users from your contacts into the app's New Chat screen. You can now begin messaging other users through the app.

It is recommended you change some settings. Under Settings » Privacy, set phone number visibility to “nobody,” and “Who can me find by number” to Everyone for ease of communication. If this is set to “nobody,” your contacts will have to be added to Signal manually on your device.

App security should be configured with a screen lock and inactivity timeout. Privacy » Advanced » Censorship Circumvention in the app settings allows you to bypass some forms of censorship if the app cannot connect directly to Signal's servers. Configurations in Settings » Data and Storage can be configured to optimize network and storage data usage.

Follow the instructions on Signal's website for desktop application installation. The mobile app must be configured first.

To link a desktop device, tap your picture at the top left of the app home-screen. Hit “Linked Devices”, and tap the plus icon. Signal Desktop will display a QR code on startup: scan this with your mobile device, confirm the link, and the app will add your desktop application to your account.