
In 2022, Slack suffered widely reported outages on February 22, March 9, July 26. After 3 PM, most of the core features became operational, except for push notifications, email, and third-party integrations including Google Calendar and Outlook Calendar. From 10 AM ET until 3 PM ET users could not log in, send or receive messages, place or answer calls, and use Slack connections.

On January 4, 2021, Slack suffered a large outage that lasted several hours. In response to the attacks, Slack added two-factor authentication to its service.

In March 2015, Slack announced it had been hacked over four days in February 2015, and that some data associated with user accounts had been compromised, including email addresses, usernames, hashed passwords, phone numbers, and Skype IDs. On January 1, 2021, Slack and Salesforce announced an agreement for Salesforce to acquire the company for a value of approximately $27.7 billion. This acquisition was to provide additional search offerings of employees within a Slack workspace. In July 2020, Slack acquired Rimeto, a startup company focused on directory building. In June 2019, Slack went public through a direct public offering to reach a market value of US$19.5 billion. The companies also announced a commitment to work on integration of Slack with Atlassian services.

On July 26, 2018, Atlassian announced the shutdown of its competing HipChat and Stride, effective February 11, 2019, and the sale of their intellectual property to Slack, with Slack to assume the user bases of the services. Slack was previously compatible with non-proprietary Internet Relay Chat (IRC) and XMPP messaging protocols, but the company closed the corresponding gateways in May 2018. Īccording to Butterfield, "Slack" is an acronym standing for "Searchable Log of All Conversation and Knowledge," which he chose in 2012 to replace the previous codename, "linefeed."

Slack launched to the public in August 2013. Slack began as an internal tool for Stewart Butterfield's company Tiny Speck during the development of Glitch, an online game.
