What Is Slack? The Work Chat Built by a Game Studio

Slack is a work chat service that splits a team's conversation into "channels". If the question is when it started, the answer is its public launch on 12 February 2014; an invitation-only preview had begun six months earlier, in August 2013. It was made by Tiny Speck, a company led by Flickr co-founder Stewart Butterfield, which until then had been making an online game.

Born from a failed game

Tiny Speck's first product was Glitch, a multiplayer online game played in the browser. According to TechCrunch on 15 November 2012, Glitch had failed to attract enough players and failed to find a buyer, so it would close on 9 December, with about 30 people laid off. The same article reported that the company had developed messaging technology with uses beyond gaming, and that a smaller core team would build new products on it.

That new product was Slack. "Building Slack", a retrospective written by early Slack staff, places the public launch thirteen months after work started, nine months after an early alpha and six months after the preview began.

12 February 2014: open to everyone

TechCrunch reported on 12 February 2014 that Slack had left its limited beta and was open to anyone. The beta had started in August 2013; participating teams ranged from about 250 people down to about 10, the latter being more typical. Pricing was to be split into free and paid tiers, and one option under consideration made the most recent 10,000 messages free while charging for the older archive.

According to "Building Slack", active users grew from about 15,000 to more than 500,000 in the first year, and the company raised US$42.75 million and became a private company valued at US$1.1 billion.

2019: a listing without new shares

Slack filed its registration statement (S-1) with the US Securities and Exchange Commission on 26 April 2019. These are the figures it reported:

The listing used no underwriters: existing shareholders could simply sell their shares on the exchange. The S-1 itself calls this a "novel method". According to The Register, trading began on the NYSE under the ticker WORK on 20 June 2019, and against a reference price of US$26 set by the exchange, the shares opened at US$38.50.

Salesforce buys Slack

On 1 December 2020 Salesforce announced a definitive agreement to acquire Slack. Each Slack share would receive US$26.79 in cash and 0.0776 shares of Salesforce stock, an enterprise value of about US$27.7 billion based on Salesforce's closing price on 30 November 2020. After the deal Slack would become an operating unit of Salesforce, still led by Butterfield.

The acquisition closed on 21 July 2021. Salesforce's announcement said Slack would continue to operate under the Slack brand, led by its CEO and co-founder Butterfield. He did not stay long: according to TechCrunch, it emerged in December 2022 that Butterfield would step down as CEO in January 2023, succeeded by the Salesforce executive Lidiane Jones.

The buyer, Salesforce, built its business by selling customer relationship management (CRM) software as a web service with nothing to install; its origins are in the Salesforce article.

Disputes over data and AI

After the acquisition, the question that came to the fore was who could use the conversations stored in Slack, and for what.

In May 2024 a passage in Slack's privacy principles drew fire. According to TechCrunch on 17 May 2024, Slack used customer data by default to train "global models" that power channel and emoji recommendations and search results, and opting out required sending the company an email. Internet Archive captures showed the clause had applied since at least September 2023. Slack said it did not train the large language models (LLMs) behind Slack AI, its paid add-on, on customer data, and a Slack engineer acknowledged that the clause predated Slack AI and needed updating.

In 2025 the rules changed for outside services that use Slack data. According to an explainer by the law firm Hunton Andrews Kurth on 5 August 2025, Salesforce revised Slack's API terms to prohibit bulk export of data available through the APIs, the creation of persistent copies or indexes, and the use of such data in LLMs. Glean, an AI service for searching across company documents, told its customers the change would hamper their ability to use their data with the AI platform of their choice; under the new terms, access was allowed only query by query.

A front door for AI agents

Salesforce has been recasting Slack as the place where staff call up AI agents. According to SD Times, a rebuilt Slackbot became generally available to Business+ and Enterprise+ customers from 13 January 2026. Salesforce says it draws on context from Slack and connected tools to find answers, organise work and schedule meetings, and shows each user only what their permissions allow.

What Slack brought in 2014 was the habit of talking about work in channels rather than by email. Twelve years on, the conversations piled up in those channels have become something companies fight over as material for AI. For other lines of messaging see WhatsApp and the origins of email; for the wider story, the internet and web timeline.