Slack Technologies, LLC
Company History
Slack History: Founding, Growth & Key Milestones
Founded 2009 in San Francisco, California, United States
When was Slack founded?
Slack was founded in 2009 in San Francisco, California, United States by Stewart Butterfield, Cal Henderson, Eric Costello and Serguei Mourachov, making it 17 years old.
- Founded
- 2009
- Founding place
- San Francisco, California, United States
- Founders
- Stewart Butterfield, Cal Henderson, Eric Costello and Serguei Mourachov
- Headquarters today
- San Francisco, California, United States
- Milestones documented
- 12 (2009–2026)
- Current CEO
- Rob Seaman (EVP & General Manager)
- Acquisitions
- 4
| Year | Event |
|---|---|
| 2009 | Tiny Speck Founded in San Francisco |
| 2012 | Glitch Closes & Internal Chat Pivots to Slack |
| 2013 | Private Beta Launch Earns 8,000 Signups in 24 Hours |
| 2014 | Official Public Launch & Fast-Track Unicorn Status |
| 2015 | $2.8 Billion Valuation |
| 2017 | Launch of Slack Enterprise Grid for Fortune 500 |
| 2019 | NYSE Direct Listing (WORK) |
| 2020 | Salesforce Announces $27.7B Acquisition Agreement |
| 2021 | Acquisition Closes & Integration with Salesforce Begins |
| 2023 | Denise Dresser Appointed CEO & Launch of Slack AI |
| 2025 | Dresser Departs; AI Bundled Into Plans |
| 2026 | Slackbot Becomes a Personal AI Agent |
- Where was Slack founded?
- Slack was founded in San Francisco, California, United States in 2009.
- Who founded Slack?
- Slack was founded by Stewart Butterfield, Cal Henderson, Eric Costello and Serguei Mourachov.
- When did Slack start?
- Slack was founded in 2009.
- How old is Slack?
- Slack is 17 years old as of 2026.
Founding Story
In 2009 Stewart Butterfield, who had co-founded Flickr, started Tiny Speck with Eric Costello, Cal Henderson and Serguei Mourachov to build Glitch, a browser-based multiplayer game. The team built an internal chat tool to work across offices. Glitch shut down in late 2012, and the founders decided the chat tool was worth more than the game. They launched a preview of Slack in August 2013, and the product launched publicly in February 2014.
Founders
Stewart Butterfield
Stewart Butterfield co-founded Tiny Speck in 2009 and led its pivot from the game Glitch to Slack. He was Slack's CEO through its 2019 direct listing and the 2021 Salesforce acquisition, and stepped down after announcing his departure in December 2022. Stewart Butterfield was born in 1973 in Lund. Education: Clare College; St. Michaels University School.
Cal Henderson
Cal Henderson co-founded Slack in 2009 (originally Tiny Speck). Before Slack, he co-founded Flickr alongside Stewart Butterfield. As an absolutely brilliant technical architect, he built the incredibly complex real-time messaging infrastructure capable of handling millions of concurrent enterprise users without dropping a single message, serving as CTO for over a decade. Cal Henderson was born in 1981.
Eric Costello
Eric Costello co-founded Slack in 2009. Having previously worked with Butterfield and Henderson at Flickr, he helped build the absolutely critical early client-side architecture for the failed video game 'Glitch,' which ultimately pivoted into the massively successful Slack desktop application. (Exact birth year remains publicly undisclosed).
Serguei Mourachov
Serguei Mourachov co-founded Slack in 2009. Another veteran of the Flickr engineering team, he played an absolutely vital role in building the early backend systems for the company's failed gaming venture, providing the technical foundation that was rapidly repurposed into the enterprise messaging app. (Exact birth year remains publicly undisclosed).
Key Milestones
Tiny Speck Founded in San Francisco
Stewart Butterfield and co-founders established Tiny Speck to build multiplayer game Glitch.
Source: en.wikipedia.orgGlitch Closes & Internal Chat Pivots to Slack
Glitch ceased operations, prompting the team to commercialize their internal communication utility.
Source: en.wikipedia.orgPrivate Beta Launch Earns 8,000 Signups in 24 Hours
Released private beta preview, igniting viral word-of-mouth adoption across Silicon Valley tech startups.
Source: en.wikipedia.orgOfficial Public Launch & Fast-Track Unicorn Status
Launched publicly, reaching a $1.1B valuation in eight months as the fastest-growing enterprise app in history.
Source: en.wikipedia.org$2.8 Billion Valuation
Slack raised $160 million in April 2015 at a $2.8 billion valuation.
Source: en.wikipedia.orgLaunch of Slack Enterprise Grid for Fortune 500
Introduced Enterprise Grid, unlocking large-scale deployments for IBM, Target, and Capital One.
Source: en.wikipedia.orgNYSE Direct Listing (WORK)
Listed directly on the New York Stock Exchange on June 20, 2019.
Source: en.wikipedia.orgSalesforce Announces $27.7B Acquisition Agreement
Marc Benioff announced Salesforce's landmark $27.7 billion acquisition of Slack to create Customer 360's digital HQ.
Source: en.wikipedia.orgAcquisition Closes & Integration with Salesforce Begins
Salesforce completed the acquisition on July 21, 2021.
Source: en.wikipedia.orgDenise Dresser Appointed CEO & Launch of Slack AI
Denise Dresser succeeded Lidiane Jones in December 2023 as Slack AI and Canvas rolled out.
Source: en.wikipedia.orgDresser Departs; AI Bundled Into Plans
Slack folded AI features into paid plans in 2025, and Denise Dresser left for OpenAI in December.
Source: techcrunch.comSlackbot Becomes a Personal AI Agent
Slackbot reached general availability in January 2026, followed by 30 AI features announced in March.
Source: techcrunch.comMajor Acquisitions
Rimeto
2020Employee directory and org-chart software.
Astro Technology
2018AI-assisted email and calendar app.
Missions (from Robot & Pencil)
2018Workflow-building tool for Slack.
Screenhero
2015Collaborative screen-sharing and voice app.
Keep researching Slack
Slack Company History FAQ
When and where was Slack originally founded?
Slack was founded in 2009 in San Francisco, California, originally as a video game development studio named Tiny Speck by Stewart Butterfield, Eric Costello, Cal Henderson, and Serguei Mourachov.
What was the original product built by Tiny Speck before Slack?
Tiny Speck was created to build an ambitious web-based multiplayer game called Glitch. While building Glitch across teams in San Francisco, Vancouver, and New York, the engineers developed an internal IRC-based chat tool to communicate and share code snippets.
How did the failure of Glitch lead to the birth of Slack?
When Glitch failed to gain mainstream traction and was shut down in December 2012, Stewart Butterfield realized their internal messaging system was far more valuable than the game. Tiny Speck pivoted completely, renaming the product Slack.
What does the acronym "SLACK" stand for?
The name Slack is an acronym for "Searchable Log of All Conversation and Knowledge," reflecting its foundational mission to replace siloed internal company email with persistent, searchable channels.
When did Slack officially launch to the public?
Slack launched its private beta preview in August 2013 and officially debuted to the general public in February 2014, adding 15,000 daily active users in its first two weeks entirely through word-of-mouth viral adoption.
When did Slack go public on Wall Street?
On June 20, 2019, Slack bypassed a traditional IPO and completed a high-profile direct listing on the New York Stock Exchange under ticker WORK, opening at a market valuation of $19.5 billion.
When did Salesforce acquire Slack and for what price?
On December 1, 2020, enterprise cloud giant Salesforce announced an agreement to acquire Slack for approximately $27.7 billion in cash and stock. The blockbuster transaction closed on July 21, 2021, marking the largest acquisition in Salesforce history.
What was the impact of the COVID-19 pandemic on Slack's adoption?
The sudden global shift to remote work in 2020 triggered historic demand for digital headquarters software, accelerating Slack's paid customer base beyond 150,000 organizations and surging daily message volume into the billions.
What was Slack Connect and when did it launch?
Launched in June 2020, Slack Connect expanded channels beyond single company boundaries, allowing up to 250 separate corporate organizations (such as vendors, clients, and partners) to collaborate securely within a shared channel.
When did co-founder and CEO Stewart Butterfield depart Slack?
Stewart Butterfield stepped down as CEO of Slack in December 2022, approximately 17 months after completing the Salesforce acquisition, passing leadership to Lidiane Jones.
How has Slack evolved under Salesforce's Agentforce strategy?
Under Salesforce, Slack was transformed from a messaging chat tool into an enterprise conversational operating system for AI agents, integrating native Slackbot AI, autonomous Agentforce workers, and Model Context Protocol (MCP) connectors.
Who currently leads Slack within Salesforce?
Rob Seaman serves as Executive Vice President and General Manager of Slack, having taken over operational leadership in December 2025 following the departure of Denise Dresser to OpenAI.
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