Slack

Slack is a cloud-based team messaging and collaboration platform. At its core, it organises conversations into channels (public or private), with direct messages and group chats for smaller discussions. Beyond messaging, Slack offers huddles (lightweight audio and video calls with AI-generated notes), Canvas (persistent documents embedded in channels), and Workflow Builder (no-code automation).

The platform integrates with over 2,600 third-party apps through its App Directory, covering everything from project management to CRM to developer tools. Since the Salesforce acquisition, Slack has added AI features including message summarisation, channel recaps, and an AI-powered search that can surface information across your workspace.

Slack's target market spans from small startups to large enterprises, though it's particularly popular with technology and knowledge-worker teams. Nearly 80% of Fortune 100 companies use Slack. For SMBs, it's a strong choice if your team prefers chat-based communication over email, especially if you need to connect multiple tools into a single conversational interface.

Slack offers four tiers. The free plan gives you unlimited users but limits message history to 90 days and caps you at 10 app integrations, which is restrictive for any serious use. Messages older than one year are permanently deleted on the free plan.

The Pro plan sits around US$7 to $8 per user per month (billed annually) and removes the message history and integration limits. This is where most small teams should start. Business+ runs about US$12 to $15 per user per month and adds SAML single sign-on, compliance exports, and bundled Slack AI features.

Enterprise Grid is custom-priced for large organisations needing multi-workspace management, advanced security controls, and dedicated support. The pricing isn't published, but expect a significant step up. Annual billing provides meaningful discounts over monthly across all paid tiers.

Vendor lock-in risk with Slack is moderate to high, depending on your plan. The core concern is that years of team conversations, decisions, and institutional knowledge accumulate in Slack and don't transfer cleanly to any alternative. There's no standard format for messaging history that works across platforms.

On the free plan, lock-in is particularly sharp because messages older than one year are permanently deleted, and you can only export public channels. Even on paid plans, getting a full export (including private channels and DMs) requires Business+ or higher with explicit approval from Slack.

The integration ecosystem creates additional soft lock-in. If you've built workflows, connected a dozen apps through Slack, and your team's muscle memory is built around Slack's interface, switching to Teams or another platform means rebuilding all of that. None of this is unusual for a messaging platform, but go in with eyes open. If data retention matters to your business, start on a paid plan from day one.

Slack was born out of a failed video game. Stewart Butterfield's studio Tiny Speck built an internal chat tool while developing a game called Glitch. When the game shut down in 2012, the chat tool became the product. Slack launched publicly in 2013 and grew rapidly, becoming synonymous with workplace messaging.

Salesforce acquired Slack in July 2021 for approximately US$27.7 billion. Under Salesforce ownership, Slack has been positioned as the front door to the Salesforce ecosystem, with deep integrations into Salesforce CRM, AI features, and the new Agentforce platform. Slack currently has roughly 3,000 employees.

The company's trajectory is worth watching. Slack's CEO Denise Dresser departed in December 2025 to join OpenAI, and several other senior Salesforce executives left around the same time. Salesforce has also been reducing headcount across divisions as it leans into AI automation. None of this signals that Slack is going away (it's too central to Salesforce's strategy for that), but the leadership churn is notable. Salesforce is publicly traded (NYSE: CRM) and profitable, so the platform itself is stable for the foreseeable future.

Slack's API is mature and well-established, built around a Web API for querying and acting on workspace data, and an Events API for receiving real-time notifications when things happen. There's also Socket Mode for development or firewalled environments where you can't expose a public endpoint.

For most integration scenarios, the API is pleasant to work with. Posting messages, creating channels, managing users, and building interactive bots are all well-documented with plenty of examples. The Bolt SDK framework (available in Python, JavaScript, and Java) handles much of the boilerplate like authentication and event routing.

Rate limits are adequate for internal custom apps built for your own workspace. Where things get tricky is for third-party tools not listed in Slack's App Directory. In May 2025, Slack dramatically reduced rate limits for non-Marketplace apps, particularly for reading message history. If you're building internal tools, this doesn't affect you. But if you rely on niche third-party integrations, verify they're Marketplace-listed or you may hit walls.

Slack supports incoming webhooks for sending messages (simple, just POST JSON to a URL) and the Events API for receiving events via HTTP callbacks. The Events API is well-designed and covers a wide range of workspace events. The main friction is needing a publicly reachable HTTPS endpoint, which is standard for webhook-based systems. Outgoing webhooks exist but are deprecated in favour of the Events API.

This is Slack's weakest area, particularly on the free plan. Free plan users can only export public channel messages, and messages older than one year are permanently deleted, even if you later upgrade. That's a genuine lock-in risk if your team accumulates important knowledge in Slack without a paid plan.

On Pro plans, you get public channel exports. Business+ adds compliance exports that can include private channels and DMs, though enabling this requires approval from Slack. Enterprise Grid offers full export controls. Export format is JSON, which is technically portable but requires tooling to make human-readable.

Importing data into Slack from other platforms is supported but limited. If you're migrating from another messaging tool, expect to lose some history or formatting in the transition. The bigger concern is that years of institutional knowledge locked in Slack conversations doesn't transfer cleanly to any alternative platform.

Documentation is above average. Slack migrated from api.slack.com to docs.slack.dev in 2025, and the new site is comprehensive with method references, event catalogues, tutorials, and SDK guides. The official SDKs for Python, JavaScript, and Java are well-maintained, and the Bolt framework is a genuinely useful starting point for new integrations.

Slack offers developer sandboxes through the Slack Developer Program, providing full Enterprise Grid environments for testing. You can have up to two active sandboxes with three workspaces and eight users each, active for six months and renewable. For simpler needs, creating a free workspace for testing works fine.

The main frustration developers report is deprecation churn. Between 2024 and 2025, Slack retired the files.upload endpoint, killed legacy bots, began sunsetting classic apps, and migrated its entire documentation platform. Each change is reasonable on its own, but the cumulative maintenance burden is real. Plan for ongoing upkeep of any Slack integration.