Open-source WhatsApp alternatives

Telegram Desktop is the official desktop client for the Telegram messaging service. The repository holds the complete source code and build instructions for an app built on the Telegram API and the MTProto secure protocol. It is written in C++, and the license is GPLv3 with an OpenSSL exception.

Builds are published for 64-bit and 32-bit Windows 7 and above, including portable versions, for macOS 10.13 and above, and for Linux as a static 64-bit build, a Snap and a Flatpak. Older systems are served by version 4.9.9, the last release that supports macOS 10.12 and older Linux with glibc. The client connects to Telegram's hosted service rather than a server you run yourself, so using it means having a Telegram account.

This repository holds the official source code for the Telegram messaging app on Android. Telegram describes itself as a messenger focused on speed and security that is free to use. The code is written in Java and published under the GPL-2.0 license, alongside compilation instructions for developers.

Developers are invited to use Telegram's API and this code to make their own applications, subject to conditions: obtain your own API id, avoid using the Telegram name or standard logo, follow the security guidelines, and publish your code to comply with the licenses. The build supports reproducible builds with dummy keystore and Firebase files that must be replaced before releasing your own APKs. Compiling needs Android Studio, the Android NDK and SDK, and cloning with submodules. Protocol documentation is available for the Telegram API and MTProto.

Signal Android is the source code of the Signal private messenger for Android. Signal describes itself as a simple and secure messenger that sends messages and places voice and video calls over WiFi or a mobile data connection, with privacy protections always switched on. The app is written in Kotlin and released under the AGPL-3.0 license, and it is free to use.

The app is available from the Play Store and signal.org, with versions for iOS and desktop as well. The repository explains how to report bugs on GitHub, join the beta channel on Google Play, contribute translations through the community forum, and submit code. New contributors are encouraged to start with small bug fixes, and larger ideas should be discussed on the community forum first. The client depends on Signal's own hosted service, so there is no self-hosted server option here.

SimpleX is a messaging network built around the idea that it should not assign identifiers of any kind to its users, not even random IDs, which the project says makes it private by design. The goal is to protect not just message content but also metadata, meaning who talks to whom and when.

Messages use double-ratchet end-to-end encryption with an additional encryption layer. Apps are available for Android and iOS, with an iOS TestFlight preview that gets new features a week or two earlier but is limited in the number of users, and a terminal client runs on Linux, macOS and Windows. The README invites readers to install the app, connect to the team and user groups, make a private connection with a friend, help with translations and donate. The core is written in Haskell.

SimpleX Chat is licensed under AGPL-3.0, and its protocol and server software are open so that others can host relays. It is aimed at people who need stronger privacy guarantees than mainstream messengers provide, such as journalists, activists and privacy-conscious individuals.

Signal Desktop is the desktop version of the Signal private messenger for Windows, macOS and Linux. It links to the Signal app on an Android or iOS phone, which lets you send and read messages from your computer. It is written in TypeScript and released under the AGPL-3.0 license.

Both a production version and a beta version can be installed. Support is provided through a support site with answers to common questions and a community forum, which is also where feature requests and questions go, while bugs are reported as GitHub issues. Contributions are welcome, including non-code ones, and the repository has a contributing guide.

Signal is run by an independent 501(c)(3) nonprofit, the Signal Technology Foundation, and donations can be made from inside the apps or on the web. The repository includes a cryptography notice explaining that the software contains encryption and may be subject to import, possession and export rules in some countries.

Signal iOS is the iPhone and iPad client of Signal, a free and open-source messaging app made for simple, private communication with friends. The same service is also available on Android and as a desktop application, so conversations are not tied to a single platform.

The app is written in Swift. The maintainers state that it collects no analytics or telemetry, which is why they rely on bug reports sent through the Support Center to troubleshoot problems. Developers can follow BUILDING.md to set up a build environment and read the contribution guidelines, while ideas and discussion go through the community forum run for Signal Foundation projects.

The repository is released under the AGPL-3.0 license. Because the software includes cryptographic functionality, the README carries a cryptography notice reminding users to check their country's rules on encryption software and documents its export classification. Signal itself operates as a hosted messaging service rather than something you run on your own server.

Signal-Server is the backend that supports the Signal Private Messenger applications on Android, Desktop and iOS. It is the server counterpart to the open-source Signal clients and is published so the way the service works can be inspected.

The project is written in Java and uses FoundationDB, so building it requires the FoundationDB client library to be installed on the host. Protocol documentation lives on signal.org/docs, and security issues are reported privately by email to the Signal security address. The maintainers say they cannot provide direct technical support, but an unofficial community forum helps people run the software in their own environment.

The code is licensed under the GNU AGPLv3 and carries a cryptography notice reminding users to check their country's rules on encryption software, along with the export classification. It is mainly of interest to developers, researchers and anyone who wants to review or experiment with the server behind Signal.

Element Android, also called Element Classic, is a previous-generation Matrix collaboration client for Android provided by Element. It runs on Android devices with Lollipop (API 21) or newer. The README says this client is still supported and receives security updates, but no new features or usability improvements are being made, and it recommends the next-generation Element X app instead. The code is written in Kotlin and licensed under AGPL-3.0.

The project is built on a new Android SDK written entirely in Kotlin, which shares the repository with the app during early development. At each release the SDK module is copied to the matrix-android-sdk2 repository so that third-party apps can use it as a regular Gradle dependency. The README also explains the delay between a GitHub release and its appearance on Google Play and F-Droid, which includes beta periods and store reviews.

FluffyChat is a nonprofit, open-source client for the Matrix network, written in Flutter. Its goal is to be an easy-to-use instant messenger that is open source and accessible to everyone. Because it speaks the Matrix protocol, it works with Matrix accounts and servers rather than a proprietary service of its own.

Users can send all kinds of messages, images and files, record voice messages, share locations and take part in video calls with Matrix RTC. It supports push notifications, unlimited private and public group chats, public channels, spaces, custom emotes and stickers, and moderation tools covering the Matrix feature set. Privacy features include end-to-end encryption, encrypted chat backup, emoji verification and cross-signing, and it follows Material You design.

For organizations, configuration can be pushed to Android and iOS devices through mobile device management since version 2.10.0, and on the web through a config.json file. Building from source requires Flutter and Rust. It is licensed under AGPL-3.0, with translations handled through Weblate and installation instructions on the project website.

This repository contains the Android client app and SDK source for Wildfire IM (野火IM), an instant messaging and real-time audio and video solution maintained by Beijing Wildfire Network Technology. It is intended for secondary development or integration into existing apps. The documentation is in Chinese, and the input lists the license only as other.

Wildfire IM is described as a professional-grade solution with private deployment, a broad feature set, support for all platforms, and easy integration with third-party systems. The family of repositories includes the IM server, this Android app, and an iOS counterpart. Topics mention chat, IM, and VoIP.

An important notice in the README says that, because of anti-fraud compliance requirements, the default protocol stack in this project only connects to the official Wildfire service and cannot connect to self-deployed servers. Users must contact the vendor to obtain a temporary or unrestricted version and replace a library file. This limits its use as a fully independent open-source client.