Slack
Headquarters
San Francisco, CAFounded
2009CEO / Founder
Rob SeamanEmployees
1001-5000Funding
Acquired — $1.4BProducts
1 product listedAvg. AI Score
7.2/10Website
slack.com
Profile updated
About Slack
Slack Technologies develops workplace communication software that organizes team conversations into channels, direct messages, and file sharing capabilities. The company was founded in 2009 by Stewart Butterfield, Eric Costello, Cal Henderson, and Serguei Mourachov in San Francisco, California, initially as a gaming company called Tiny Speck before pivoting to workplace collaboration tools in 2013.
Slack's platform serves as a digital workspace where teams can communicate through organized channels, share files, and integrate with third-party applications including Google Drive, Zoom, and Salesforce. The service is used by organizations ranging from small startups to Fortune 100 companies including IBM, Target, and Airbnb. Slack competes with Microsoft Teams, Discord, and other workplace communication platforms.
Salesforce acquired Slack in July 2021 for $27.7 billion, making it one of the largest software acquisitions in history. Prior to the acquisition, Slack had raised approximately $1.4 billion in funding across multiple rounds and went public in 2019 through a direct listing on the New York Stock Exchange. The company employed approximately 2,500 people at the time of acquisition.
Specialties
Financials
Dated, source-cited figures. Estimates are marked.
Products by Slack
All products by Slack reviewed by our AI panel of experts.
How Our Review Panel Scores Slack
Six independent reviewer personalities assessed Slack's product on their own terms. They disagreed by 3.7 points — The Skeptic was the hardest to convince, The Decision Maker the most positive.
Averaged across 1 reviewed product in our catalog. Scores are out of 10.
Competitive Landscape
Who Slack competes with, and how they differ.
Microsoft bundles Teams free with Microsoft 365 subscriptions, undercutting Slack on price for enterprises already paying for Office; Slack filed an EU antitrust complaint against Microsoft in 2020 over this bundling.
9 products reviewed on TopReviewed
Discord grew out of gaming communities around always-on voice channels and public/semi-public servers, versus Slack's channel-based, primarily private workspace model built around enterprise IT admin controls and compliance.
Mattermost is open-source and self-hostable, targeting security- and compliance-sensitive organizations (government, defense) that want on-premise deployment rather than Slack's SaaS-only model.
Google Chat ships bundled into Google Workspace alongside Gmail and Meet, competing on the same integrated-suite logic as Microsoft Teams rather than as a standalone product like Slack.
6 products reviewed on TopReviewedCompany Timeline
Key milestones in Slack's history, with sources.
- Partnership
Salesforce makes Anthropic's Claude the default model for Slack AI
Salesforce announced Anthropic's Claude as the default reasoning model across Agentforce and Slackbot, deepening an AI partnership that brings Claude-powered agents into Slack workflows.
usine-digitale.fr - Launch
Slack adds Agentforce task-specific AI agents
Slack introduced Agentforce integration, letting teams deploy task-specific AI agents directly inside Slack channels and workflows.
en.wikipedia.org - Milestone
Denise Dresser named Slack CEO
Denise Dresser replaced Lidiane Jones as Slack CEO, continuing leadership turnover following Stewart Butterfield's 2022 departure.
en.wikipedia.org - Partnership
Slack partners with OpenAI for ChatGPT integration
Slack announced a partnership integrating OpenAI's ChatGPT into the platform for AI-assisted search, summarization and writing.
en.wikipedia.org - Milestone
Stewart Butterfield departs as Slack CEO
Co-founder Stewart Butterfield stepped down as Slack CEO under Salesforce ownership; Lidiane Jones was appointed to succeed him.
en.wikipedia.org - Launch
Slack launches Huddles
Slack introduced Huddles, lightweight audio-first (later video-capable) conversation channels aimed at replacing ad hoc calls.
en.wikipedia.org - Acquisition
Salesforce completes acquisition of Slack
Salesforce closed its acquisition of Slack, folding the messaging platform into Salesforce's portfolio as a standalone brand and integration hub.
en.wikipedia.org - Acquisition
Salesforce announces $27.7B acquisition of Slack
Salesforce announced an agreement to acquire Slack for approximately $27.7 billion in cash and stock, its largest acquisition ever at the time.
en.wikipedia.org - Funding
Slack goes public via NYSE direct listing
Slack Technologies went public through a direct listing on the NYSE, opening at a valuation of roughly $19.5 billion, bypassing a traditional IPO roadshow.
en.wikipedia.org - Acquisition
Slack acquires HipChat and Stride from Atlassian
Slack acquired the intellectual property behind Atlassian's HipChat and Stride messaging products, shutting both down and migrating interested customers to Slack.
en.wikipedia.org - Launch
Slack launches publicly
Slack launched publicly, drawing roughly 8,000 signups within 24 hours; it emerged from Stewart Butterfield's failed multiplayer game Glitch, whose internal chat tool became the product.
en.wikipedia.org - Founded
Tiny Speck founded by Stewart Butterfield
Stewart Butterfield founded Tiny Speck to build the online game Glitch; when Glitch shut down in 2012, the team pivoted to commercialize its internal communication tool, which became Slack.
en.wikipedia.org
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