Slack is described as 'Facilitates teams' real-time collaboration with versatile chat interface and advanced search in configurable channels across multiple platforms' and is a leading Group Chat app in the social & communications category. There are more than 100 alternatives to Slack for a variety of platforms, including Web-based, Android, iPhone, Windows and Mac apps. The best Slack alternative is Element. It's not free, so if you're looking for a free alternative, you could try Element or Zulip. Other great apps like Slack are Rocket.Chat, Discord, Matrix and Trello.
AirSend is a simple collaboration space for professionals and small teams that brings all your conversations, files, notes, and to-do lists into one place so that you can get work done faster and easier.
Lightweight communication platform with unlimited channels, seamless voice and video, screen sharing, private file sharing, advanced task and calendar tools, robust privacy features, emoji and thread support, and multi-platform efficiency for gaming or team communities.
Basecamp is a web-based project collaboration tool that allows groups of people to share files, meet deadlines, assign tasks, and centralize feedback.
A comprehensive collaboration platform within Office 365, providing centralized chat, file sharing, and HD video meetings. Accessible on multiple platforms, it offers enterprise-grade security and compliance, customizable notifications, and private to group chat sessions.
Peer-to-peer group chatting over Tor and IPFS, with local-first encrypted messaging and no central servers, offers privacy-focused decentralized collaboration for teams, supporting desktop and mobile. FOSS, open to contributors, and avoids surveillance-based tracking.
Conversations is a privacy focused, open source XMPP Texting [Jabber] client for Android 4.0+ smart phones with wife-approved easy encryption [OTR, OMEMO, or GPG].
Twist is a team communication service that emphasizes conversation organization and work relevance. It does so in a way that promotes asynchronous communication for more thoughtful discourse.
Twake is a real-time teamwork platform. It is a suite of collaborative tools that includes the specificities of some bestsellers (Slack, Trello, Google Drive...). We provide professional messaging, storage space, online collaborative editors (Words, Excel, PowerPoint), task...
Powered by WebRTC, Real-time video call, chat room and screen sharing entirely browser based.
Self-hosted communication platform with secure audio, video, chat, web conferencing, screensharing, advanced encryption, and metadata privacy, running on user-controlled servers, supporting web and mobile apps, and eliminating third-party data exposure.
Open-source platform unifying project, document, issue, and task management with real-time team collaboration, instant messaging, video conferencing, and GitHub bidirectional sync, all in one customizable workspace for developers and product teams.
Transform team work habits with an intuitive platform offering customizable workflow solutions, enterprise-grade security with certifications, and features that imbue data ownership, ensuring privacy and control across global processes.
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Slack limits itself to specific workspaces of teams. If you want to communicate between organizations or teams, shared channels are hard to setup and manage. AirSend doesn't have those issues.