Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
TapTalk.io - TapTalk.io is a complete in-app chat SDK and messaging API - Easy integration and customizeable.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Lets Chat - Open source self-hosted chat app for small teams
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
WeChat API - WeChat API and SDK allow developers to access and integrate the functionality of WeChat with other applications.