Slack is a channel-based workplace messaging platform owned by Salesforce, Inc. (NYSE: CRM), which bought it for $27.7 billion in July 2021. Founded in 2009 as Tiny Speck by Stewart Butterfield, Eric Costello, Cal Henderson and Serguei Mourachov, Slack reported $902.6 million in revenue in fiscal 2021, its last year as a public company. Rob Seaman, EVP and general manager, leads Slack.
What Does Slack Do?
- Channels and messaging: persistent, searchable channels by team, project or topic, plus direct messages and threads.
- Huddles: quick audio and video calls with screen sharing.
- Slack Connect: shared channels between separate companies.
- Canvas, Lists and Workflow Builder: documents, task tracking and no-code automation inside Slack.
- Slackbot and AI: summaries, AI search and a personal AI agent, generally available since January 2026.
- App Directory: more than 2,600 apps, including Google Drive, Jira and Salesforce.
How Does Slack Make Money?
Slack sells per-user subscriptions. The free plan keeps 90 days of message history. Pro is listed at $8.75 per user per month billed monthly ($7.25 billed annually), with Business+ and enterprise plans adding administration, compliance and security controls. In 2025 Slack stopped selling its separate Slack AI add-on and built AI features into paid plans. Salesforce also sells Slack alongside its CRM clouds and Agentforce.
Slack Revenue and Financials
Slack's revenue grew from $400.6 million in fiscal 2019 to $630.4 million in fiscal 2020 and $902.6 million in fiscal 2021 (year ended January 31, 2021). That year it posted an 86.5% GAAP gross margin, a $283.1 million GAAP operating loss, $62.2 million in free cash flow and a 123% net dollar retention rate, with 156,000 paid customers. Salesforce has not reported Slack revenue separately since the acquisition; in March 2026 Marc Benioff said Slack revenue had grown about 2.5 times and that about a million businesses run on Slack.
Who Owns Slack?
Salesforce announced the deal on December 1, 2020 and closed it on July 21, 2021. Slack shareholders received $26.79 in cash and 0.0776 Salesforce shares per share, valuing Slack at about $27.7 billion. It was Salesforce's largest acquisition.
Who Runs Slack?
Stewart Butterfield ran Slack until announcing his exit in December 2022. Lidiane Jones led it for most of 2023, and Denise Dresser from December 2023 until she left to become OpenAI's chief revenue officer in December 2025. Rob Seaman, previously chief product officer, then took charge and was named EVP and GM of Slack in February 2026.
Origins
Tiny Speck built the browser game Glitch, which shut down in December 2012. The team's internal chat tool became Slack, which opened as a preview in August 2013 and launched publicly in February 2014. Slack listed directly on the NYSE under ticker WORK on June 20, 2019.
Competitors
Slack's main rivals are Microsoft Teams, Google Chat, Zoom Workplace, Cisco Webex and Mattermost. In 2020 Slack filed an EU antitrust complaint over Microsoft bundling Teams with Office 365; Microsoft unbundled Teams worldwide in 2024 and the European Commission accepted its commitments in 2025.
2026: Slack as an AI Agent Hub
Salesforce made Slackbot generally available as a personal AI agent on January 13, 2026. On March 31, 2026 it announced 30 more AI features, including reusable AI skills, meeting transcription and summaries, and MCP client support that lets Slackbot hand work to Agentforce and other agents.
