The core difference
Slack was built as a standalone messaging tool. It does one thing — team communication — and does it well. Channels are clean. Threading works. Search is fast. The interface has barely needed to change since launch because it got the fundamentals right the first time. When it came to integrations, Slack built an app directory early and let third-party developers run with it. There are now more than 2,600 integrations. If your business runs on tools outside the Microsoft ecosystem — Salesforce, HubSpot, Asana, GitHub, Stripe, whatever — Slack connects to them without much friction.
Microsoft Teams was built to replace email inside organizations that already use Office. It pulls Word documents, Excel spreadsheets, SharePoint sites, and Outlook calendars directly into the platform. A Teams meeting is already on your Outlook calendar. A document you edited in Word is available in the Teams channel without uploading it. For businesses running entirely on Microsoft 365, that depth of integration is genuinely useful. For businesses using other tools, it adds complexity without much return.
The other difference worth naming: Teams is more complex. The relationship between teams, channels, and tabs is not immediately obvious to new users. Slack's model — workspaces, channels, direct messages — is simpler. For IT and MSP teams with dedicated administrators, that complexity is manageable. For small accounting firms or law offices where the office manager is also the IT department, Slack's lower setup burden matters.
"If you're already paying for Microsoft 365, Teams is essentially free. If you're not, Slack is easier to set up and easier to keep organized."
Quick comparison: Slack vs Microsoft Teams
| Feature | Slack | Microsoft Teams |
|---|---|---|
| Free tier | Yes — 90-day message history, 10 app limit | Yes — limited features |
| Paid entry | Pro $7.25/user/mo (billed annually) | Included in Microsoft 365 Business Basic ($6/user/mo) |
| Mid-tier | Business+ $12.50/user/mo | Microsoft 365 Business Standard $12.50/user/mo |
| Enterprise | Enterprise Grid — custom pricing | Microsoft 365 Business Premium $22/user/mo |
| Video calling | Available — not the main focus | Strong — core feature with full meeting tools |
| Integrations | 2,600+ third-party apps | Strong within Microsoft ecosystem, fewer external |
| Office 365 integration | Partial — via connectors | Native — Word, Excel, SharePoint, Outlook built in |
| Search | Fast, reliable, with filters | Decent, can be slower on large orgs |
| Interface complexity | Simpler — easy onboarding | More complex — steeper learning curve |
| Best for | Startups, tech teams, mixed-tool environments | Microsoft 365 shops, larger orgs with IT support |
Pricing: what you actually pay
Slack's free tier is real — you can run a small team on it — but the 90-day message history limit is the thing that kills it for growing businesses. Anything older than three months disappears from search. That is fine for a 3-person startup. It is a problem for an 8-person team trying to find a decision made six months ago.
Pro at $7.25/user/month unlocks full message history and removes the 10-app integration cap. Business+ at $12.50 adds compliance exports, user provisioning, and 24/7 support with a 4-hour response time guarantee. Most small and mid-size businesses land on Pro.
Slack pricing reality check: A 10-person team on Slack Pro pays $72.50/month ($870/year). That same team on Microsoft 365 Business Basic — which includes Teams — pays $60/month ($720/year) and also gets Exchange, OneDrive, and SharePoint. If you are already considering Microsoft 365 for email and storage, Teams becomes essentially a free add-on.
Microsoft Teams pricing only makes sense in the context of Microsoft 365. You do not buy Teams standalone for a business — you buy Microsoft 365 and Teams comes with it. Business Basic ($6/user/month) includes Teams, Exchange email, OneDrive, and SharePoint. Business Standard ($12.50/user/month) adds the desktop Office apps — Word, Excel, PowerPoint, Outlook. Business Premium ($22/user/month) adds advanced security and compliance features most small businesses do not need yet.
The value calculation is straightforward: if you need Microsoft 365 anyway, Teams is free. If you do not need Microsoft 365, Teams is not worth buying just for messaging.
Slack deep dive
Slack's strength is its integration ecosystem. More than 2,600 apps connect directly to Slack — not through clunky webhooks that need a developer, but through proper integrations that take minutes to set up. GitHub sends a message when a pull request is reviewed. PagerDuty alerts the on-call engineer in their personal DM. Stripe notifies the sales channel when a payment clears. HubSpot pings the account owner when a deal moves stages. The integrations are shallow — Slack is the notification layer, not the action layer — but they keep the right information in front of the right people without anyone having to check a dashboard.
Threading is genuinely better in Slack than in Teams. In Slack, you reply in a thread and the channel stays clean. In Teams, threads inside channels can get confusing — it is not always obvious which messages are replies and which are new topics. For fast-moving teams with high message volume, that difference adds up across a week.
Search in Slack is fast and reliable. You can search by person, channel, date range, file type, and keyword. On a Business+ plan, every message ever sent is searchable. For teams that rely on finding past decisions or old specifications, that matters.
Slack's Huddles feature — lightweight audio calls you drop into with one click — has become genuinely useful for quick questions that would take ten messages to resolve. It is not trying to replace Zoom for formal meetings. It is replacing the "can you hop on a quick call?" message.
Limitations worth knowing:
- The free tier's 90-day message history limit is a real constraint for any team that needs to reference older conversations or audit decisions.
- Slack is not trying to replace email. External communication with clients or vendors still lives in email. Teams has a similar limitation, but the Microsoft ecosystem gives it Outlook as a complement.
- Notification management requires discipline. Slack's defaults will interrupt your team constantly. Every new user needs to configure do-not-disturb schedules and notification keywords or they will drown in pings.
- At scale — 500+ person companies — Slack can become expensive fast. Enterprise Grid pricing is custom and typically runs significantly higher than Teams at the same headcount.
Microsoft Teams deep dive
Teams' biggest advantage is not a feature — it is economics. If your business already pays for Microsoft 365, you have Teams. Adding Slack on top means paying twice for communication. Most businesses that have evaluated the overlap and chosen Teams have done so for this reason alone, not because Teams is strictly better at messaging.
Where Teams actually earns its place: video calls. Teams was built with video meetings as a first-class feature. Breakout rooms, meeting recordings saved to SharePoint, live transcription, whiteboards, polls — it is a full meeting platform. Slack's video features are an afterthought by comparison. If your team runs a lot of formal meetings — client calls, all-hands sessions, department reviews — Teams' meeting tooling is meaningfully better.
Document collaboration inside Teams is a legitimate differentiator. Open a Word document inside a Teams channel and multiple people can edit it simultaneously, with comments visible in context. No file uploads, no version confusion, no switching apps. For teams that spend significant time reviewing and editing documents together, that workflow is faster than anything Slack offers.
SharePoint integration means Teams channels can have dedicated file repositories that are automatically organized, versioned, and searchable. For businesses that deal with large volumes of contracts, proposals, or reports, that structure is useful from day one.
Limitations worth knowing:
- The interface has improved but remains more complex than Slack. New users regularly get confused about the difference between a team, a channel, a chat, and a tab. Onboarding without IT guidance takes longer.
- Search in Teams can be slower, especially in larger organizations with extensive file libraries. Slack wins on message search speed.
- Third-party integrations outside the Microsoft ecosystem are fewer and often less polished than Slack's equivalents. If your stack includes tools that Slack supports natively — and most do — you may find the Teams version requires more workarounds.
- Teams is less suited to external communication with collaborators outside your organization. Guest access works, but it adds friction for people not already in the Microsoft ecosystem.
"Teams wins on video meetings and Office document collaboration. Slack wins on everything else — interface, search, threading, and third-party integrations."
Who each platform is actually for
Choose Slack when: Your team uses a mix of third-party tools and wants them all connected to a central communication hub. You are a startup or tech company where UX and developer integrations matter. Your team prioritizes fast, clean messaging and strong search over deep document management. You are not currently paying for Microsoft 365 and do not plan to.
Choose Teams when: You are already paying for Microsoft 365 and use Word, Excel, Outlook, and SharePoint regularly. Your team runs formal video meetings as a core part of the workflow. You have an IT department or administrator who can configure Teams properly. You are a larger organization where Microsoft's compliance and governance tools matter.
The overlap to acknowledge: For many basic communication needs — channels, direct messages, file sharing, quick calls — both platforms do the job. The decision points are usually pricing (do you already pay for Microsoft 365?) and ecosystem fit (where does your other work happen?). Teams is not worse than Slack; it is built for a different environment.
The decision framework
Five honest questions before you commit to either:
- Are you already paying for Microsoft 365? If yes, Teams is included and adding Slack means paying for redundant messaging. Unless your team has a compelling reason to use Slack specifically, that is hard to justify.
- How many third-party tools does your team use? CRM, project management, billing, support, development tools — if you use more than a handful of non-Microsoft apps and want them feeding information into your messaging platform, Slack's 2,600+ integrations are a real advantage.
- How important are video meetings to your workflow? Internal quick calls and informal video chats work fine in either. If you run formal client meetings, all-hands sessions, or heavily-structured internal reviews, Teams' meeting tooling is the better platform.
- Who is going to set this up and manage it? Slack takes an afternoon to configure for a small team. Teams benefits significantly from proper administration — someone who understands the teams/channels/tabs structure and sets it up intentionally. If nobody on your team is going to do that, Teams will end up messier than Slack on the same timeline.
- How technical is your team? This is not about intelligence — it is about tolerance for interface complexity. Non-technical teams consistently find Slack easier to learn and stick with. Technical teams adapt to either. For real estate offices, dental practices, or cleaning businesses where the staff is not especially tech-oriented, Slack's simpler model wins on adoption alone.
The automation gap neither platform closes
Both Slack and Teams handle internal communication well. Channels stay organized. Notifications get routed correctly. Files get shared. People can find each other fast. That is what they are built for, and they both do it.
Neither platform connects automatically to the external business systems where real work starts and ends.
A new client signs a contract in your CRM. That should create a dedicated Slack channel for the project, invite the account team, and post the contract details as a pinned message. It does not — not without custom wiring. A job gets marked complete in your field service software. That should ping the billing person in Teams so they can send the invoice. It does not. A new employee gets added to your HRIS. That should automatically create their accounts, invite them to the right channels, and send them an onboarding message. Also does not happen on its own.
These are not edge cases. They are the moments where information needs to move between systems automatically — and neither Slack nor Teams, no matter which plan you are on, builds those connections for you. Both offer webhooks and an API. Neither offers a pre-built integration that ties your CRM client record to a new Slack channel on contract signature.
Building exactly that — the cross-system wiring that connects external events to the right internal communication — is what Aplos AI does. We build on top of whichever messaging platform a business already uses. We do not ask you to switch. We close the gaps the platform leaves open.
Using Slack or Teams but still manually pinging the team when a new client signs or a job wraps up? We build the automations that do it for you — from CRM to channel to the right person, without the copy-paste.
Get a Free Automation Audit →The verdict
If you are already running on Microsoft 365, use Teams. Full stop. The economics do not favor adding Slack, and Teams is good enough at messaging for most teams. Invest the time in setting it up properly and it will not let you down.
If you are not in the Microsoft ecosystem — or if you are evaluating both as a fresh choice — Slack is the better product for most small and mid-size businesses. It is easier to set up, easier to keep organized, faster to search, and better connected to the third-party tools your team probably already uses. The $7.25/user/month Pro price is fair for what you get.
What neither platform does is connect your communication to the rest of your business automatically. A signed contract is still an email someone reads and then manually relays to the team. A completed job still requires someone to write the channel message. Those handoffs are where time gets lost — and where automation actually makes a difference.