How to Delete Slack Messages
Locate the message you want to delete in Slack.
Hover over the message, and click on the three-dot icon that appears to the right of the message.
From the dropdown menu, select “Delete Message.”
A confirmation pop-up will appear to ensure you want to delete the message. Click “Delete” to remove it permanently.
Note that you can only delete your own messages unless you are an admin or have special permissions in the workspace.