Slack brings all your communication together in one place
Easy to integrate with Excellent interface on multiple platforms Free People really enjoy using it
Supercharge team collaboration with group chat and IM
Integrates well with a lot of developer tools Developer-friendly Clients for every major platform Free unlimited users
Open source slack alternative
Open source Can be deployed on premise Faster than Slack Byos (bring your own server)
Open-source, self-hosted, Slack alternative
Open source On-premise deployment Free Built using golang
Chat-based workspace in Office 365
Free Well-thought Design Work well with the rest of Office 365 work flow Mobile friendly
Powerful open source team chat
Open source Great Community Extensive developer documentation Clean & Smooth UI
Flowdock is your team's chat with a shared inbox. Teams using Flowdock react in seconds and never forget anything.
Threaded chat Simpler integrations than others, team inbox = awesome Great interface Extremely easy to manage multiple conversations
A messaging platform built for teams
Free
Slack for the whole world, except end-to-end encrypted across all your devices
KBFS Encypted Git repos End-to-End encryption
Group messaging & video meetings for teams, from Atlassian
A faster way for your team to communicate
Open source team messaging application with apps for Android, iOS, and Web
Your own business messenger.
Mobile friendly Email compatibility Easy to use Free
Team collaboration with real time chat.
Easy to use Minimalist Integrations with CI servers etc
Slack without the annoying distractions
A community platform for the future.
Real-time business chat & texting for teams
Free Github integration Bitbucket integration Apps for many platforms
Open source self-hosted chat app for small teams
Open source Docker, Vagrant, NodeJS BYOS XMPP Support
Like Slack except P2P, offline friendly, and open source
A modern and Open Source Web client for XMPP
A small alternative to Slack
Chat interoperability-as-a-service