Slack's help pages don't publish a fixed cap on workspace members. What they do limit is how people get in: each invite link lasts 30 days and works for up to 400 people, email invitations last 30 days, and invites can be throttled if many go unaccepted. Free workspaces, as of Nov 2026, also carry usage limits.
If you're planning a community, a course group or a fast-growing team, the member question usually comes up early. The short answer is that the help pages describe no headcount ceiling. The limits that matter are on the way in.
The limits that apply to getting people in
| Item | Limit | Applies to |
|---|---|---|
| Invite link lifetime | 30 days | Each invite link |
| People per invite link | Up to 400 | Each invite link |
| Email invitation lifetime | 30 days | Each emailed invitation |
| Message and file visibility | Last 90 days | Free workspaces, as of Nov 2026 |
| Third-party or custom apps | Up to 10 | Free workspaces, as of Nov 2026 |
| Retention options | Keep one year or delete after 90 days | Free workspaces, set by owners |
Invite links for big groups
An invite link is active for 30 days and can be used by up to 400 people. For a webinar audience or a cohort, that's the quickest way in: share the link, and people join without you sending a single email. When a link runs out of uses or days, make a new one.
A few conditions apply. Invite links are available on the free, Pro and Business+ plans, as of Nov 2026. They aren't shown if single sign-on is switched on, and they can't be created in the Android app.
The throttle that stops email invites
Here's the wall most people hit. According to the Slack Help Center article on inviting new members, Slack may limit your ability to send invitations, typically when you've sent many invites and few have been accepted. Revoking the pending invites doesn't lift the limit, and the pending ones stay valid while it's in place.
So if you paste a list of 300 addresses from a spreadsheet and half of them are old, you could find yourself unable to invite anyone for a while. The documented way round it: share an invite link instead of sending more emails. Clean the list before you send, and use the link for anything large.
Email invitations themselves last 30 days. Owners and admins can resend a pending invitation to bring it back to life. This guide on inviting someone to Slack walks through the screens.
Who's allowed to invite
By default, members can invite new members. Owners and admins can change that so invitations need admin approval; members then request invitations instead of sending them. For a community where you want to control who joins, that's the setting to switch on before you share the workspace widely.
Guests are separate. Owners and admins can invite guests and set a time limit on their accounts, which suits freelancers and clients on a fixed project. Guests can't be invited from the mobile apps, so do that from a computer.
What a free workspace caps instead
A free workspace doesn't cap members either, but it does cap what those members can see and connect, as of Nov 2026. Messages and files from the last 90 days can be viewed and searched; older material is hidden, and items over a year old are permanently deleted. Owners can choose to keep everything for one year, or delete it after 90 days. A free workspace can also add up to 10 third-party or custom apps.
For a large community, the 90-day window matters more than the member count, because useful answers from three months ago drop out of search.
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How Teams sets a hard number
Microsoft Teams documents a maximum of 25,000 members in a team, with 10,000 in an org-wide team. If a fixed, published ceiling matters for your planning, that's a difference worth weighing; my list of team chat apps compares the wider options.
My advice for growing a workspace fast
Use invite links, not bulk email, for anything over a handful of people, and refresh them every 30 days or 400 joins. Switch on admin approval if you want a gate. Clean any address list before you send email invites, because a throttle caused by dead addresses won't clear when you revoke them. On a free workspace, pin or save the answers people need, since anything older than 90 days drops out of view.
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Frequently asked questions
Is there a maximum number of members in a Slack workspace?
The help pages don't state a fixed member cap; they document invite limits and free workspace limits instead.
How many people can use one invite link?
Up to 400, and the link is active for 30 days.
Why can't I send more invites?
Invitations may be limited when many have been sent but few accepted. Share an invite link instead.
Do free workspaces have other limits?
Yes: 90 days of visible messages and files and up to 10 apps, as of Nov 2026.
Can guests be added from the mobile app?
No. Guests can't be invited from the mobile apps.
