Franz - Free messaging app for services like WhatsApp, Slack, Messenger and many more

•    Javascript

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Franz is a messaging app that combines chat & messaging services into one application. Franz currently supports Slack, WhatsApp, WeChat, Facebook Messenger, Telegram, Google Hangouts, GroupMe, Skype and many more. Franz allows you to add each service many times. This makes Franz the perfect tool to manage multiple business and private accounts all at the same time. You could even use five different Facebook Messenger accounts at once, if some inexplicable reason urges you to do so.

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Rambox - Messaging and Emailing app that combines common web applications into one

•    Javascript

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Rambox is a messaging and emailing app that combines common web applications into one. It gives you the possibility to add common services many times you need, all in one place. It's perfect for people who work with many services for business and private accounts.

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community-edition - Free and Open Source messaging and emailing app that combines common web applications into one

•    Javascript

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Free and Open Source messaging and emailing app that combines common web applications into one.

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Signal-Android - A private messenger for Android, alternative to WhatsApp

•    C

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Signal is a messaging app for simple private communication with friends. Signal uses your phone's data connection (WiFi/3G/4G) to communicate securely, optionally supports plain SMS/MMS to function as a unified messenger, and can also encrypt the stored messages on your phone.

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integrations - Connect your App to Multiple Messaging Channels with the W3C Open standard.

•    Javascript

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Connect your App to Multiple Messaging Channels in a Single Integration with W3C Open standard. Broid Integrations is an open source project released by Broid that allows you to easily converse on all the major communication platforms (messaging & voice) without integrating each API.

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Slackin - Public Slack organizations made easy

•    Javascript

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Slackin is a little server that enables public access to Slack server. It is like Freenode but on Slack.

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Gitter - Community for Software Developers

•    Javascript

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Gitter is designed to make community messaging, collaboration and discovery as smooth and simple as possible. You can easily create, organise and grow your communities, inviting others to join just in one click. Gitter is an instant messaging and chat room system for developers and users of GitHub repositories. Gitter is similar to IRC and Slack. Unlike IRC, and like Slack, it automatically logs all messages in the cloud.

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chat - Instant messaging server - backend in Go, client-side binding in Java and Javascript

•    Go

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Instant messaging server. Backend in pure Go (license GPL 3.0), custom client-side binding in Java including Android and Javascript (license Apache 2.0), as well as gRPC client support for C++, C#, Go, Java, Node, PHP, Python, Ruby, Objective-C. Wire transport is JSON over websocket or gRPC over plain TCP (long polling is also available). Persistent storage RethinkDB.Tinode is meant as a replacement for XMPP. Overall it's a lot like open source WhatsApp or Telegram.

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Elixir-Slack - Slack real time messaging and web API client in Elixir

•    Elixir

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This is a Slack Real Time Messaging API client for Elixir. You'll need a Slack API token which can be retrieved from the Web API page or by creating a new bot integration. Add Slack to your mix.exs dependencies function.

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slack-ruby-client - A Ruby and command-line client for the Slack Web and Real Time Messaging APIs.

•    Ruby

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A Ruby client for the Slack Web and RealTime Messaging APIs. Comes with a handy command-line client, too. If you are not familiar with these concepts, you might want to watch this video. You're reading the documentation for the next release of slack-ruby-client. Please see the documentation for the last stable release, v0.12.0 unless you're integrating with HEAD. See UPGRADING when upgrading from an older version.

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python-slackclient - Slack Developer Kit for Python

•    Python

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A basic client for Slack.com, which can optionally connect to the Slack Real Time Messaging (RTM) API.Whether you're building a custom app for your team, or integrating a third party service into your Slack workflows, Slack Developer Kit for Python allows you to leverage the flexibility of Python to get your project up and running as quickly as possible.

slack slack-api library

messaging-apis - Messaging APIs for multi-platform

•    Javascript

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Messaging APIs is a mono repo which collects APIs needed for bot development. It helps you build your bots using similar API for multiple platforms, e.g. Messenger, LINE. Learn once and make writing cross-platform bots easier.

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Lets-Chat - Self-hosted chat for small teams

•    Javascript

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Let's Chat is a persistent messaging application that runs on Node.js and MongoDB. It's designed to be easily deployable and fits well with small, intimate teams. It supports XMPP Multi-user chat (MUC), Multiple rooms, File uploads and lot more.

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Applozic-Android-SDK - Android Real Time Chat & Messaging SDK

•    Java

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Open source Android Chat SDK / Messaging SDK that lets you add real time chat and in-app messaging in your mobile (android, iOS) applications and website. Signup at https://www.applozic.com/signup.html to get the application key.

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Beaver - 💨A real time messaging server to build a scalable in-app notifications, multiplayer games, chat apps in web and mobile apps

•    Go

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A Real Time Messaging Server. Beaver is a real-time messaging server. With beaver you can easily build scalable in-app notifications, realtime graphs, multiplayer games, chat applications, geotracking and more in web applications and mobile apps.

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PyFCM - Python client for FCM - Firebase Cloud Messaging (Android, iOS and Web)

•    Python

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Firebase Cloud Messaging (FCM) is the new version of GCM. It inherits the reliable and scalable GCM infrastructure, plus new features. GCM users are strongly recommended to upgrade to FCM. Using FCM, you can notify a client app that new email or other data is available to sync. You can send notifications to drive user reengagement and retention. For use cases such as instant messaging, a message can transfer a payload of up to 4KB to a client app.

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Briar - Secure messaging, anywhere

•    Java

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Briar is a messaging app designed for activists, journalists, and anyone else who needs a safe, easy and robust way to communicate. Unlike traditional messaging tools such as email, Twitter or Telegram, Briar doesn't rely on a central server - messages are synchronized directly between the users' devices. If the Internet's down, Briar can sync via Bluetooth or Wi-Fi, keeping the information flowing in a crisis. If the Internet's up, Briar can sync via the Tor network, protecting users and their relationships from surveillance.

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braid - Braid is a team-chat app with a novel UI that leads to better conversations.

•    Clojure

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Braid is an experimental team chat application with a novel UI: instead of chatrooms, it's based on many short conversations. You can think of Braid as an email/mailing-list/web-forum/chatroom hybrid, but without the constant interruptions and FOMO of Slack. It's particularly good for remote-first companies, developer teams and online communities. Braid is also open-source, so you can hack on it and host your own version. You can read more about Braid and then give Braid a try.

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SlackKit - Build Slack apps, in Swift

•    Swift

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SlackKit makes it easy to build Slack apps in Swift. It's intended to expose all of the functionality of Slack's Real Time Messaging API as well as the web APIs that are accessible to bot users. SlackKit also supports Slack’s OAuth 2.0 flow including the Add to Slack and Sign in with Slack buttons, incoming webhooks, slash commands, and message buttons.

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Atlas-Android - Library of native Android chat and messaging UI components, built to work with Layer

•    Java

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Use our new XDK! The XDK enables a richer messaging experience and new features will be added there. See the repository at https://github.com/layerhq/Android-XDK. Don't worry, Atlas-Android will still be supported in the meantime. Atlas is an open source framework of customizable UI components for use with the Layer SDK designed to get messaging tested and integrated quickly. This repository contains the Atlas library. For a fully-featured messaging app, see the open source Atlas Messenger project, which uses this Atlas library and the Layer SDK.