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Launch the Slack app. Sign in to your team. Open the team menu. Tap the name of the channel you want to enter. Find the user name of the team member. Type /remove [user] into the text box. Tap the Send icon (the paper airplane).
If you are a Team Admin or Owner, you can remove another team member from a Slack channel with a simple text command. Tap “Slack” on your home screen or app drawer to begin.  As long as the channel is public, a removed member can rejoin whenever they want. They will also still be able to view files and channel history. If the channel is private, a removed member cannot view channel files or history unless they are re-added by someone in the channel. If you’re not already signed in to your team, enter your team name, email address, and password when prompted to access your team’s default channel (usually #general). Note that you cannot remove someone from #general (or other default team channels). Swipe in from the left to view the team menu. The channel will open, and its name (e.g., “#channel”) will appear at the top of the window. In the mobile app, you have to use a text command to remove a user by name. To find the member’s user name:  Tap the name of the channel. The channel details screen will appear. Tap “Member List.” The user names are listed here in alphabetical order. Scroll until you find the person you want to remove, then make note of that name. Replace “[user]” with the user name of the team member you want to remove. The team member is no longer in the channel. Another way to remove a member is to type “/remove [username] into the text box and press ↵ Enter.