signalapp/signal-server

★ 10,543JavaAudience · developerComplexity · 5/5LicenseSetup · hard

Mindmap

mindmap
  root((signal-server))
    What It Does
      Delivers encrypted messages
      Manages user accounts
      Coordinates client apps
    Tech Stack
      Java backend
      Maven build tool
      FoundationDB storage
    License
      GNU AGPLv3
      Modifications must be shared
    Audience
      Security researchers
      Backend contributors
      Protocol studiers

mindmap root((signal-server)) What It Does Delivers encrypted messages Manages user accounts Coordinates client apps Tech Stack Java backend Maven build tool FoundationDB storage License GNU AGPLv3 Modifications must be shared Audience Security researchers Backend contributors Protocol studiers

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Things people build with this

USE CASE 1

Study the server architecture of a production end-to-end encrypted messaging system for research or education.

USE CASE 2

Contribute bug fixes or security improvements to the open-source code that powers the real Signal service.

USE CASE 3

Use the codebase as a reference for building your own end-to-end encrypted communication backend.

USE CASE 4

Run the test suite to verify server logic before submitting a code contribution.

Tech stack

JavaMavenFoundationDB

Getting it running

Difficulty · hard Time to first run · 1day+

Requires FoundationDB installed on the host machine before building, no guided self-hosting support is provided by the project.

You can use and modify this software, but any modified version you distribute must also be made available under the same open-source terms.

In plain English

This repository contains the server-side software that powers Signal, the encrypted private messaging application used on Android, iOS, and desktop. Signal is known for end-to-end encryption, meaning that messages are encrypted on the sender's device and can only be decrypted by the recipient, with the server never able to read the contents. This repository is the backend that coordinates message delivery, account management, and other server-level functions between Signal's client apps. The README is intentionally minimal. It points to the official Signal documentation website for protocol details, provides a single command to build and run tests using Maven (a standard Java build tool), and directs security reports to a dedicated email address. The server depends on FoundationDB, a distributed database system developed by Apple and open-sourced, which must be installed on the host machine before building. Signal has made the server code available under the GNU AGPLv3 license, which is a strong open-source license requiring that modifications also be made available under the same terms. However, the project does not offer direct technical support for people running their own instances. Community help is available through an unofficial forum linked in the README. The README includes a standard cryptography export notice, which is a legal statement required when distributing software that contains encryption. It informs users that export laws vary by country and that they should check local regulations before using or redistributing the software. This is a routine inclusion for software of this type rather than a sign of unusual legal complexity.

Copy-paste prompts

Prompt 1

Walk me through building and running the signal-server test suite using Maven on a Linux machine.

Prompt 2

How does signal-server use FoundationDB for message storage? Explain the data model based on the codebase.

Prompt 3

I want to contribute to signal-server. Which parts of the codebase handle message delivery between clients?

Prompt 4

What does the AGPLv3 license mean for someone who wants to run a modified version of signal-server?

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