Top Alternatives to Riot.im

Skype is an instant messaging and VOIP (Voice Over Internet Protocol) client to communicate with people in a distant place.

Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Hangouts is an instant messaging software developed by Google.

Telegram is a free cloud-based instant messaging platform.

WhatsApp Messenger is an instant messaging platform owned by Facebook.

Slack is a cloud-based team collaboration tool.

Adium is an Open source multi-protocol instant messaging client for Mac OS X, supports MSN, Jabber, Yahoo! and other networks.

Mumble is an open source, low-latency, high quality voice chat software primarily intended for use while gaming.

Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.

Trillian is a proprietary multiprotocol instant messaging application.

Viber Free Messenger and Phone Calls.

Discord is a freeware proprietary VoIP application designed for gaming communities.

Signal is the most scalable encryption tool.

Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.

Imo free video calls and chat is a kind of Communication apps for Android.

Facebook Messenger is the official Facebook app that lets you have text conversations with all of your friends on the popular social network.

Empathy is an instant messaging (IM) and voice over IP (VoIP) client which supports text, voice, video, file transfers, and inter-application communication over various IM protocols.

TeamSpeak is software for quality voice communication via the Internet.

IM+ supports simultaneously major IM services, including Google Talk, Twitter DMs, Yahoo!, AIM/iChat, ICQ, Jabber (and Slack through Jabber), etc.

LINE is a new communication app which allows you to make free voice calls and send free messages whenever and wherever you are.

RetroShare is open source software for encrypted filesharing, serverless email, instant messaging, online chat, and BBS, based on a friend-to-friend network built on GNU Privacy Guard (GPG).

Mattermost is an open source, private cloud Slack-alternative, Workplace messaging for web, PCs and phones. MIT-licensed.

Wire is a cross-platform, encrypted instant messaging client created by Wire Swiss. It is available for iOS, Android, Linux, Windows, macOS and Web browser clients.

Kopete is a multi-protocol, free software instant messaging client released as part of the KDE Software Compilation. Although it can run in numerous environments, it was designed for and integrates with the KDE Plasma Workspaces.

Ring (SFLphone) is an open-source SIP-compatible softphone and instant messenger for Linux, Microsoft Windows, OS X and Android.

ICQ is an open source instant messaging software.

FaceTime is a proprietary videotelephony product developed by Apple Inc. FaceTime Audio is an audio-only version.

WeChat is a social media with instant messaging, commerce and payment services application.

Rocket.Chat free open source chat solution.

ChatSecure is a messaging application for iOS which allows OTR and OMEMO encryption for the XMPP protocol.

Kik Messenger is an instant messenger software.

Off-the-Record Messaging (OTR) is a cryptographic protocol that provides encryption for instant messaging conversations.

Xabber (XMPP and Jabber) is a XMPP client for the Android Operating System.

Threema is an encrypted instant messaging application for iOS, Android and Windows Phone.

Bitmessage is a decentralized, encrypted, peer-to-peer, trustless communications protocol that can be used by one person to send encrypted messages to another person, or to multiple subscribers.

Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with users of a different service provider via online chat, Voice over IP, and Videotelephony.

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.

TorChat is a decentralized anonymous instant messenger that uses Tor hidden services as its underlying network. It provides cryptographically secure text messaging and file transfers.

KakaoTalk (Korean: 카카오톡), or sometimes KaTalk, is a free mobile instant messaging application for smartphones with free text and free call features.

BlackBerry Messenger, also known as BBM is an instant messenger and videotelephony application included on BlackBerry devices that allows messaging and voice calls between BlackBerry, iOS, Android, and Windows Mobile users.

Conversations is an open source XMPP/Jabber client for the Android platform.

TribeScale is an All-in-One platform to coordinate your team around what really matters - communication, goals, decisions, tasks and results.

Flock is a communication app for teams. Packed with tons of productivity features, Flock drives efficiency and boosts speed of execution.

Grape is an REST-like API framework for Ruby. It's designed to run on Rack or complement existing web application frameworks such as Rails and Sinatra by providing a simple DSL to easily develop RESTful APIs.

Google Duo is a video chat mobile app available on the Android and iOS operating systems.

Tencent QQ (QQ) is an instant messaging software service.

Jitsi Meet is an open-source (Apache) WebRTC JavaScript application that uses Jitsi Videobridge to provide high quality, scalable video conferences.

Bit Chat is a secure, peer-to-peer, open source instant messenger with end-to-end encryption.

GroupMe is a mobile group messaging app.

Zulip is a chat and collaborative software.