Overview
By default, Slack may allow members to share files externally by generating public URLs that anyone can access without signing in. Disabling this ensures files shared in Slack can only be accessed by members of your workspace, preventing sensitive content from being exposed publicly.
Prerequisites
Slack Pro or Business+ plan
Slack admin access
Instructions
From your desktop, click Admin in the sidebar
Select Workspace settings from the menu
Click the Permissions tab
Next to Public File Sharing, click Expand
Ensure Enable public file URL creation is unchecked
Click Save
