Signal Desktop — End-to-End Encrypted Messaging for Desktop

Introduction

Signal Desktop is the official desktop companion to the Signal private messenger. It extends Signal's end-to-end encryption protocol to Linux, macOS, and Windows, allowing you to send and receive messages, media, voice notes, and video calls from your computer. Signal is developed by the non-profit Signal Technology Foundation with a focus on privacy and open-source transparency.

What Signal Desktop Does

• Sends and receives end-to-end encrypted text, image, video, and voice messages
• Supports group chats with up to 1000 members, all end-to-end encrypted
• Provides disappearing messages with configurable expiration timers
• Syncs message history with a linked mobile device over an encrypted channel
• Enables voice and video calls from the desktop application

Architecture Overview

Signal Desktop is built with Electron and TypeScript. It uses the Signal Protocol (Double Ratchet algorithm with X3DH key agreement) for end-to-end encryption, implemented via libsignal-client (written in Rust with bindings to Node.js). Messages are stored in a local SQLite database encrypted with SQLCipher. The app communicates with Signal's servers only for message routing and key exchange; servers never have access to plaintext content.

Self-Hosting & Configuration

• Download official builds from signal.org or install via platform package managers
• Signal Desktop must be linked to an existing Signal mobile account via QR code pairing
• On Linux, official packages are available for Debian/Ubuntu (apt) and Flatpak
• Message data is stored locally and encrypted; no cloud backup of desktop messages exists
• Proxy support is available for users in regions where Signal is blocked

Key Features

• Uses the Signal Protocol, widely regarded as the gold standard for end-to-end encryption
• Sealed sender feature hides metadata about who is messaging whom from Signal servers
• Built-in note-to-self feature for saving private notes across devices
• Keyboard shortcuts and notification controls for power users
• Full source code is open and auditable under the AGPL-3.0 license

Comparison with Similar Tools

• Telegram Desktop — Faster and more feature-rich for groups, but only Secret Chats are end-to-end encrypted; Signal encrypts everything by default
• WhatsApp Desktop — Uses the Signal Protocol but is closed source and owned by Meta with broader data collection
• Element (Matrix) — Decentralized and self-hostable; Signal is centralized but simpler to use with stronger default privacy
• Slack/Discord — Designed for teams and communities; Signal is designed for private person-to-person and small group messaging
• Wire — Also end-to-end encrypted and open source, but has a smaller user base and a commercial focus

FAQ

Q: Can I use Signal Desktop without a phone? A: No. Signal Desktop must be linked to a Signal account on a mobile device. The phone handles initial registration and key generation.

Q: Is Signal Desktop open source? A: Yes. The full source code is available on GitHub under the AGPL-3.0 license.

Q: Does Signal Desktop store messages locally? A: Yes. Messages are stored in a local SQLCipher-encrypted SQLite database on your computer.

Q: Can I self-host a Signal server? A: The server code is open source, but self-hosting requires maintaining your own infrastructure and would create a separate network incompatible with the main Signal network.

Sources

• https://github.com/signalapp/Signal-Desktop
• https://signal.org/