The short answer
- Already paying for Google Workspace or Microsoft 365? Chat and meetings are included, so a separate Slack Pro seat at $8.75/user/mo may be a duplicate: modeled first-year saving $80 per seat. the math
- Slack Free keeps 90 days of message history, 1:1 huddles only and up to 10 apps, and deletes data older than a year. slack.com
- Self-hosting Mattermost is modeled to cost $1,355 more than Slack in year one for a single seat once upkeep counts; it only pays with a larger team. the math
- Stay on Slack if Slack Connect channels with customers, Workflow Builder or years of searchable history matter to you. slack.com
Four ways to stop paying for Slack
A cheaper vendor
Cheaper plan Slack (free tier): saves $93 in year one (+4 more below)
Open source
Mattermost: costs $1,355 more in year one (+2 more below)
An agent skill
Nothing in the catalog fits this job yet.
Replace with AI
Nothing in the catalog fits this job yet.
The best option of each kind, modeled, not measured: each figure links its math. Keeping Slack is a valid answer too.
Who should switch, and who shouldn't
Switch if
- You already pay for Google Workspace or Microsoft 365 for email and documents: Chat and Meet, or Teams, come with them. the math
- Your team is small, 90 days of searchable history is enough, and huddles are mostly 1:1. slack.com
- You have someone who already runs servers and a team big enough that per-seat fees add up: Mattermost is free to self-host. the math
What Slack costs today
List prices from the vendor's pricing page, as stored in the Stackcut catalog. Each price links its source.
| Plan | Billed monthly | Billed yearly (per month) | What you get |
|---|---|---|---|
| Slack Pro | $8.75/user/mo | $7.25/user/mo | Unlimited message history and apps; group huddles (up to 50 people, 25 on video); group Slack Connect |
| Slack Business+ | $18/user/mo | $15/user/mo | Everything in Pro plus advanced AI, SAML SSO, SCIM; huddles up to 50 people |
The alternatives, ranked
8 ways out, ranked by modeled saving in the first year after setup and upkeep (8 priced). Modeled, not measured: each figure links the math on the recipe page.
- Paths are modeled per seat against Slack Pro at $8.75/user/mo. The Workspace and Microsoft 365 paths assume you already pay for those suites. recipe
Compare a specific alternative
Considering a specific destination? Read its checked comparison before deciding what to move.
- Slack vs Mattermost Checked migration details, public switching accounts.
What team chat costs at 1, 5 and 20 users
Every paid option here is per user. The suites include email, storage and documents, so compare them only if you'd buy them anyway.
| Option | List price | 1 user | 5 users | 20 users |
|---|---|---|---|---|
| Slack Pro today | $8.75/user/mobilled monthly | $8.75 | $43.75 | $175 |
| Slack Business+ today | $18/user/mobilled monthly | $18 | $90 | $360 |
| Slack Free90 days of history | $0free plan | $0free tier | $0free tier | $0free tier |
| Google Workspace Business Starterincludes Chat and Meet | $8.40/user/mobilled monthly | $8.40 | $42 | $168 |
| Microsoft 365 Business Basicincludes Teams | $7/user/mobilled yearly | $7 | $35 | $140 |
| Mattermost (self-hosted) | $0 licenseAGPL-3.0 source, MIT for its builds | $0+ your server | $0+ your server | $0+ your server |
How people actually left Slack
4 public accounts of leaving Slack: 3 switched, 1 went back. Summaries are ours; each links the original, and each was checked against its page before it appeared here.
A 5-person team that moved from Slack to self-hosted Mattermost years ago (over the 90-day free-history limit) got caught by Mattermost's v11 free-tier changes: upgraded into the limited Entry edition, lost access to chats beyond 10k messages, and documented a manual downgrade to Team Edition that preserved their data. Mattermost Discussion Forums
An office that moved from Slack to a self-hosted Mattermost hit severe delivery and notification problems; the Mattermost team replied that websockets were likely not fully installed on the instance. Much of the office reverted to email and phone. Hacker News
A counter-anecdote in the same HN thread: a ~50-user Mattermost deployment on 4.10.1 was reliable with none of the OP's delivery issues, but the UI is bare-bones and threading poorly implemented, so he treats it like IRC. Cautions that Slack migrants should not expect a 1:1 copy. Hacker News
Vendor case study: Data For Good, a 6,000-volunteer nonprofit, left Slack for self-hosted Mattermost on Docker over data sovereignty. They benchmarked Zulip and Rocket.Chat too; deployment was smooth and they plan Mattermost Enterprise as the centerpiece of a fully self-hosted tool suite. Mattermost
How to leave Slack
Export first, then cancel. Every step links the vendor's own help page, checked on the date shown.
How to leave Slack
Export first
- Public channels (messages and file links): Admin → Workspace settings → Security → Import & export data → Export (ZIP of JSON). Free and Pro export public channels only; private channels and DMs need Business+ or Enterprise. On Free, file links cover the last 90 days. slack.com
What you lose
- Canvases and Lists turn read-only
- Existing Workflow Builder workflows stop working
- Guest accounts are deactivated and Slack Connect channels disconnect
- Everyone is removed from user groups
Cancel
- Export what you need first (see export).
- Admin → Manage billing → Overview → Change plan details → Downgrade to Free.
- Workspace Owners, or the member who upgraded the workspace, can do this.
- Takes effect
- You choose: right away or on your next renewal date.
- Refunds
- Not stated for a downgrade to Free. Slack credits unused paid time only when you move from Business+ to Pro.
- After you cancel
- Free shows the most recent 90 days of messages and files, deletes data older than 1 year, allows 1:1 huddles only and up to 10 apps.
Not covered by the paths above, per the recipe: App integrations, Slack Connect (external), Workflows, Slack AI. If you rely on one of these, keep the incumbent or check the path closely.
Moving your data, destination by destination
What each destination's importer carries over, what it leaves behind, and any help it offers switchers.
To Mattermost
Official guide docs.mattermost.com · Tools: mmetl, mmctl
Moves: users (full); channels (full); message history (full); file attachments (full); threads (partial). docs.mattermost.com
Doesn't move: Slack apps, bots, slash commands, webhooks and Workflow Builder automations; Canvases; Starred conversations; User groups (recreatable via Mattermost Custom Groups); User presence, profile pictures and custom profile fields; Deactivated or deleted Slack users are not migrated. docs.mattermost.com
Watch out for:
- The import is idempotent: re-running the same posts creates no duplicates. docs.mattermost.com
- Missing user emails become @example.com placeholders the admin must fix before or after import. docs.mattermost.com
- mmetl runs on Linux/macOS only; WSL is not recommended for heavy migrations. docs.mattermost.com
Community guide linkedin.com · Tools: slack-advanced-exporter, slackdump (rusq), mmetl, mmctl
Moves: public channel messages (full); user accounts (full). linkedin.com
Watch out for:
- Slack's regular export omits emails and attachments; slack-advanced-exporter (or slackdump for private channels) is needed to fill the gaps. linkedin.com
- In Mattermost v10.5.2 the import fails unless every user is in at least one channel; patch the JSONL first. linkedin.com
- Default Max Users Per Team (50) will trip mid-import on larger workspaces. linkedin.com
Switching help: Mattermost ships free, open-source migration tooling for Slack: the mmetl CLI converts a Slack export (including Enterprise Grid) into a Mattermost bulk-import JSONL plus attachments folder, and mmctl validates, uploads and processes the import. Imports are idempotent. docs.mattermost.com
Switching help: Mattermost's official Slack migration docs state that support from a Mattermost expert is available for Slack migrations, and that support negotiating an export of customer IP from Slack Enterprise can be requested by contacting a Mattermost expert. docs.mattermost.com
Switching help: Nonprofit licensing program: $250 for 3 years, up to 1,000 users, for qualifying nonprofit organizations. Mattermost also says it is considering special pricing for smaller for-profits with under $10M USD annual operating budget. forum.mattermost.com
From each destination's own migration docs and switching pages, plus community write-ups where no official guide exists, each checked against its page. Confirm terms on the linked page before you rely on an offer.
Open-source and forkable options
- Mattermost: Free self-hosted team chat with full history. License: AGPL-3.0 source (MIT for Mattermost's own builds) · source code
- Zulip: Suits teams that can run a small server: the Apache-2.0 server is free with every feature, but mobile push notifications are free for only 10 users unless you pay $3.50/user/month (Basic). License: open_source
- Element (Matrix): Suits security-minded teams that want encrypted chat and federation with other organizations; Element aims its free Community edition at non-professional use up to 100 users, and search in encrypted rooms needs the desktop app. License: open_source
Open source means no license fee, not free to run: the server, backups and upgrades are yours. Read the license before you fork or resell; several of these are open-core or source-available.
FAQ
What do I lose if I downgrade Slack to Free?
History beyond 90 days (and data older than a year is deleted), group huddles, more than 10 apps, Slack Connect channels, guests, working Workflow Builder workflows, and editable Canvases and Lists. slack.com
Can I export private channels and DMs?
Not on Free or Pro: those plans export public channels only. Private channels and DMs need Business+ (after applying for the self-serve export tool) or Enterprise. slack.com
Do I get money back if I downgrade mid-cycle?
Slack's help page doesn't state a refund for moving to Free. You can choose to downgrade on your next renewal date instead of right away. slack.com
Keep reading
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find_alternatives({"vendor": "Slack", "seats": 5,
"features_used": ["Channels and DMs", "Huddles (calls)"]})