Slack

Description

In November 2012, Stewart Butterfield shut down a game. Glitch — a browser-based multiplayer world built by his company Tiny Speck — had spent years trying to find an audience and never quite found one. Butterfield announced the shutdown with candor: the game was not going to make it. What he did not say publicly was that Tiny Speck was not closing. Something else had grown along with the game.

The Glitch development team was spread across Vancouver, San Francisco and New York. IRC handled their communication at first, but IRC could not do what they needed — file sharing, persistent searchable history, organized topic threads. The engineers constructed their own tool. By the time Glitch was over, they had used it every day for years and found it more useful than anything else they had tried. Butterfield’s next tweet was cryptic: “you will know it well.”

The name stood for something: Searchable Log of All Conversation and Knowledge. Butterfield spent months in beta, cycling through companies that had been invited to try it, and watching where the tool broke down. A rollout to a 120-person startup went badly enough that the team rebuilt for another eight months before trying again. When the preview was launched in August 2013, 8,000 teams registered in the first 24 hours. The public release came in February 2014, and Slack generated $1 million in subscription revenue in a day. By October 2014 — eight months after launch — the company was valued at a billion dollars, then the fastest any startup had done so.

Salesforce has announced the acquisition of Slack Technologies in December 2020 for about $27.7 billion, which was completed in July 2021. Butterfield departed the company in December 2022, and was succeeded first by Lidiane Jones and then by Denise Dresser, a Salesforce executive appointed in November 2023. As of 2025, Slack has more than 750,000 organizations worldwide.

CHANNELS AND MESSAGING

Slack organizes conversations into channels — persistent chat rooms identified by a hash symbol and a name. A company will usually have channels for teams (#engineering, #marketing), projects (#launch-q3), topics (#bugs, #announcements) and social purposes (#random). Channels can be public, visible to all members of the workspace, or private, which are open to invited members.

Messages remain and remain searchable by default. On paid plans, history goes back forever; on the free tier, only the last 90 days are available. Users react to messages with emoji, reply within threads to help keep discussions on the side, and bookmark messages for later. The message composer has support for formatting and inline code rendering.

HUDDLES

Slack Huddles began as audio-only lightweight calls in March 2022 and were added to video in June 2022. Huddles open from any channel or direct message with one click, with no scheduled meeting link or calendar invite. Participants can share their screens, draw on shared screens, and have side-conversations in a linked thread during the call. The median huddle is about ten minutes long.

In 2024 and 2025, Slack introduced AI-generated notes to Huddles on paid plans: a transcript and summary of key points and action items is available after each call ends. Huddles support up to two users on the free tier and up to 50 users on paid plans.

SLACK CONNECT

Slack Connect enables members of different organizations to communicate in shared channels or direct messages without leaving their own workspaces. An account manager at one company invites a client at another; both parties see the shared channel within their own Slack in addition to internal channels. The Pro plan includes up to 250 external organizations per workspace. Compliance filters on higher tier plans scan outgoing messages for data loss prevention.

INTEGRations and Workflow Builder

More than 2,600 applications integrate with Slack via the Slack App Directory. Common integrations include Google Drive, GitHub, Jira, Asana, Zoom, Salesforce, PagerDuty and Confluence. When someone creates a pull request in GitHub or opens a ticket in Jira, Slack will post a notification to a specific channel.

Workflow Builder is a no-code editor for creating automations within Slack. Triggers include messages with certain keywords, scheduled times, form submissions or events in connected apps. Common uses include onboarding sequences that send new team members messages during their first week, daily standup forms posted to channels every morning, and incident response workflows that page the on-call engineer when a monitoring alert fires. Business+ and Enterprise+ plans support the use of conditional logic and custom functions written using Slack’s APIs.

SLACK AI

Slack started rolling out native AI features in early 2024. In June 2025, the company made a change in pricing, and basic AI tools were added to all paid plans instead of being offered as a separate add-on. Basic AI — channel and thread summaries, Huddle notes — is included with the Pro plan. More advanced capabilities require Business+ or Enterprise+.

The AI summarizes the activity of a channel over a period of time, flattens long threads to key decisions, creates daily digests across relevant channels and surfaces explanations of acronyms or jargon based on the history of conversation within the workspace. Enterprise search on Enterprise+ plans extends AI-powered search across connected applications — Google Drive, Salesforce, Jira, SharePoint, OneDrive — returning results through a single query inside Slack. Agentforce integration added in 2025 allows organizations to deploy Salesforce AI agents directly into Slack channels where team members interact with them alongside their human colleagues.

CANVAS

Canvas is Slack’s inbuilt document editor. Users create persistent documents within a workspace, attach them to channels, and collaborate on them. Canvases support rich text, checklists, live Salesforce data fields that sync bidirectionally, and files linked from connected storage services. On paid plans, AI can write canvas content from a summary of conversations on the channel or meeting notes.

PRICING

The free tier offers unlimited users and channels, but only 90-day message history, ten app integrations, and one-on-one calls in Huddles. Pro costs $7.25 per user per month billed annually and includes unlimited message history, unlimited app integrations, group huddles, Slack Connect for up to 250 organizations, Workflow Builder, and basic AI features. A minimum of three users applies to all paid plans.

Business+ is $15 per user per month billed annually with the addition of advanced AI — daily digests, file summaries, AI-built workflows — single sign-on, 99.99% uptime SLA, and SCIM provisioning. Enterprise+ pricing is custom and negotiated with Slack’s sales team; it includes unlimited workspaces under one organization, organization-wide search, enterprise key management, data retention controls, eDiscovery, and GovSlack for government deployments requiring FedRAMP and DoD Impact Level 4 compliance. Organizations that upgrade to Enterprise+ cannot downgrade.

COMPETITiveness and Market Position

Microsoft Teams exploded in popularity after its release in 2017 and accelerated during the Covid-19 pandemic when Microsoft included Teams in Office 365 at no additional cost. By 2025, Teams had about 44% of the team collaboration market share compared to Slack’s around 18.6%, a difference that was largely due to Teams being included in Microsoft 365 subscriptions that enterprises already owned. Within companies running both products, Slack tended to win engineering teams and agile organizations while Teams dominated organizations standardized on Microsoft infrastructure. Slack’s integration depth — more than 2,600 connected apps in 2025 — and enterprise client retention of more than 98% kept its place among organizations that choose it deliberately rather than by default.