Slack

Slack is a business messaging platform that organizes team communication into channels dedicated to topics, projects, or groups. Alongside channels, it offers direct messages, threaded replies, voice and video huddles, file sharing, and searchable history. A large directory of app integrations and workflow automation lets teams bring notifications and tasks from other software directly into their conversations.

It is used by companies of all sizes as a hub for day-to-day collaboration, reducing reliance on internal email. Its main strengths are organized, persistent conversations, powerful search, and an extensive ecosystem of connected apps and bots.

Slack launched in 2013, growing out of an internal tool built by a gaming company, and is headquartered in San Francisco. Since 2021 it has been owned by Salesforce. The service follows a freemium model, with paid plans adding unlimited message history, more integrations, and administrative and compliance controls.