Short answer: a customer does not join the vendor’s workspace to use a Slack Connect channel, and none of the Slack help articles read here list that as a step. The iOS and Android steps ask the customer to “choose the workspace that you’d like the channel to be part of”, so the channel lands in a workspace on the customer’s side and the customer needs a Slack account. That is our reading, because the Slack Connect article does not say whether invitees need an account. Source checks: Slack’s accept, join, Slack Connect, pending-invitation, free-teams and API pages were read on 2026-11-10, and Slack can change them.
Sort the customer into one case
- Path A: the customer already uses Slack in some workspace, on any device.
- Path B: the customer has no Slack account and the invitation arrived by email.
- Path C: the customer has only a plain link and no invitation email.
Decision rule: if they are signed in to any Slack workspace, use Path A. If they have no Slack account and hold an invitation email, use Path B. If all they have is a URL, use Path C. Do not route by button text, because the sources do not show which labels a Slack Connect email carries.
Path A: the customer already uses Slack
On desktop: from Home, click “Directories”, click “External”, click “Accept”, review the channel settings, then click “Accept and join channel”. The final click is a separate step from “Accept”, so tell the customer to expect two screens.
On iOS: tap the profile picture at the top of the screen, tap “Invitations to connect”, tap “Accept”, choose the workspace you’d like the channel to be part of, then tap “Confirm”. On Android the menu item is “Slack Connect invitations” and the other steps match.
Our recommendation, not a documented Slack step: on a phone the customer picks the workspace their colleagues use, not a personal one and not the sender’s. The desktop steps show no workspace choice, and the accept article does not say which workspace a desktop acceptance attaches the channel to. So before clicking “Accept and join channel”, the customer reads the workspace name in the Slack window and confirms it is their company’s. If they cannot tell, they accept on a phone instead.
If acceptance waits for approval, the customer’s own admin approves it, because the accept article says “Your admins may need to approve Slack Connect channel invitations you accept.” If the accept option is missing, the article’s “Owners and admins can restrict who can accept invitations” is the next thing to check with that admin. By default all members can accept, but guests and Frontline members cannot.
Signed out on desktop: go to slack.com/signin, enter the email address, click “Continue”, enter the confirmation code Slack emails, then click “Join” next to a workspace under “Accept an invitation”. That path is written for workspace invitations, so check the workspace is their own, then follow the desktop steps above. The articles give no browser steps, so if “Directories” is missing in a browser, use the app.
Path B: the customer has no Slack account
The join article describes an email invitation to a workspace. On desktop: click “Join now”, enter your full name, then click “Continue”. On iOS or Android: tap “Join now”, enter your full name, then tap “Create Account”. The article does not mention Slack Connect, and the sources read do not confirm that a Slack Connect email uses these labels. Do not give the customer these labels as the Slack Connect steps. Tell them what to check on each screen instead.
Address rule: the join article says “You can use the same email address to join as many workspaces as you’d like, but you’ll have separate Slack accounts for each one.” It does not say what happens when sign-up uses a different address. Our rule: sign up with the address the invitation was sent to.
Worked example: the invitation went to ana@acme-client.example. Ana signs up with a personal address, cannot find the invitation, and the sources give no way to change the email on that account. The fix is a new invitation to the address she used for sign-up, or to a different address she chooses with you. Ask the sender to send it.
Path C: a plain invite link
The Slack help articles read here do not describe accepting a Slack Connect channel through a plain link. The pending-invitations article covers workspace invitations and invitation links for joining a workspace, which is the outcome to avoid. That a workspace invitation puts the person in the sender’s workspace is our inference from its title and purpose, since no source states it for Slack Connect.
Our rule: if the link opens a join screen for the sender’s company, decline it and ask for an email invitation. If it opens nothing or shows an error, do not keep retrying. Ask the sender for a new email invitation.
The API docs add one case. When the emails argument is supplied, they say Slack sends “a transactional email to the recipient containing a URL that triggers joining the Slack Connect channel”. The docs do not describe the screens, so handling it like Path B is our assumption.
Expired, declined and blocked invitations
Slack’s pending-invitations article says “Invitations and invitation links will expire after 30 days.” That covers workspace invitations and links. The Slack Connect articles read give no day count, so treat a Slack Connect invitation older than 30 days as expired and ask for a new one. The 30-day threshold is our working rule for your team, not a Slack rule.
| What the customer sees | What Slack’s help says | What to do |
|---|---|---|
| Cannot accept the invitation | “Owners and admins can restrict who can accept invitations.” | Ask an owner or admin of the workspace they are accepting into. |
| Guest or Frontline account | By default all members, but not guests or Frontline members, can accept. | Use a full member account, or ask an owner or admin. |
| Waiting for approval | “Your admins may need to approve Slack Connect channel invitations you accept.” | Ask the customer’s own workspace admin to approve. |
| Offered an upgrade or free trial | The accept article says the feature is available on paid subscriptions and a non-paid workspace may see that option. | Check the free-teams setting below, then ask the customer’s admin. |
| Older than 30 days, or shows as expired | The 30-day rule is written for workspace invitations and links. | Ask the sender for a new invitation. |
| Declined | The accept article does not say what happens to a declined invitation. | Ask the sender for a new invitation. |
The plan sources conflict on the surface. The accept article says the feature is available on paid subscriptions and that a non-paid workspace may be offered an upgrade or free trial when accepting. The free-teams article says that by default free teams can join channels they’re invited to without having to upgrade or start a free trial, and that Org Owners and Org Admins can manage the setting. Our reading, which Slack does not state: the default allows free-plan acceptance, and an upgrade or trial prompt on the customer’s side suggests that setting has been changed, so their admin is the person to ask.
The sender can revoke an invitation “if it hasn’t been accepted yet”, and people with permission to manage Slack Connect channels can revoke any pending invitation sent by someone in their organization. That matters when the original sender has left: ask a Slack Connect manager on your side to revoke the stale one before sending a new one. The pending-invitations article lists “Extend invitation”, “Resend invitation” and “Delete invitation” for workspace invitations. Neither article describes these for a declined Slack Connect invitation, so ask the sender to send a new invitation.
Confirming it worked, and the wrong-workspace case
The sources do not describe where the channel should appear after acceptance or how to check it. Our check: ask the customer to post one line in the channel and tell you which workspace name sits at the top of their Slack window when they do. If the channel never shows up, treat it as not accepted and go back to the table above.
The sources give no way to move a channel or undo an acceptance, and a sender can only revoke an invitation that has not been accepted. They also do not say whether a second acceptance moves the channel or adds a second membership. Test that with one customer before you rely on it.
Decision rule: if the channel shows under a workspace that is not the customer’s company’s, follow the steps below. If it shows under their own company’s workspace, the problem is elsewhere, so go back to the Path A steps.
- Ask the customer which workspace the channel now appears under, and confirm it is not the sender’s.
- Ask the customer’s own workspace admin: “Can you see the channel #[channel] in our workspace, and can it be removed?” The sources read do not describe this, so the answer is the admin’s.
- Tell the sender the channel name and the workspace the customer accepted into. Ask for a new invitation to the same address only after the admin has answered.
The message to send the customer
Fill in the channel and vendor names, then send this as written:
“You’ve been invited to the shared Slack channel #[channel] by [Vendor]. You do not need to join [Vendor]’s workspace, so don’t if Slack or the email offers it. Use your own company’s workspace instead. If you don’t have a Slack account, open the invitation email and follow the prompts, using the email address the invitation was sent to. If a screen names a workspace, check that it is your company’s before you continue. On a computer, open your own company’s workspace, click Directories on the Home screen, click External, click Accept, check the workspace name, then click ‘Accept and join channel’. On a phone, tap your profile picture, tap Invitations to connect (Slack Connect invitations on Android), tap Accept, choose your own company’s workspace when Slack asks which workspace the channel should be part of, then tap Confirm. Your admin may need to approve the invitation. Once you’ve accepted, post one line in the channel so we know it worked. If you can’t accept it, or it shows as expired, reply to me and I’ll send a new one.”
What the sender checks
To invite someone from another company, open the channel, click the channel name in the header, go to the Settings tab, and under Slack Connect click “Add people”. Enter the email address, click “Add”, select “An external organization”, click “Next”, choose “Can post & invite” or “Can only post” if you have permission, click “Next”, add an optional note, then click “Send Invitation”.
Limits: “each Slack Connect channel can host up to 250 organizations, including your own.” Admins can restrict who may invite external people, so the option may be missing. You may be prompted to verify your email, and “Your admins may need to approve invitations you send.”
On plans, the Slack Connect article says “Available on paid plans” and names no specific plan. Through the API, conversations.inviteShared documents these errors: not_paid (“This feature is only available to paid teams.”), no_external_invite_permission (“User does not have permission to invite an external user.”) and inviter_email_not_verified (“The inviting user has not verified the email address on their own account.”). The docs also say “Only one email or one user ID may be invited at a time”, so a bulk invite script must make one call per customer contact. Confirm the sender’s plan, permission and verified email before assuming the problem is on the customer’s side.
What these sources leave open
- Which members of the customer’s workspace can see the channel after acceptance, and whether its admins get visibility. The Slack Connect article says only that “people can only access the channels they’ve been invited to join.”
- Whether a Slack Connect invitee needs a Slack account.
- Which workspace a desktop acceptance attaches the channel to.
- What happens when sign-up uses a different address from the invited one.
- Leaving a shared channel or removing access after accepting. If the customer has already accepted and wants out, the sources give no route, so say so and do not promise a process.
- Changing the email on a Slack account, and browser or mobile web behavior.