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The syncing feature allows you to access your SPO files through File Explorer even when you’re offline, providing more flexibility and reducing the time by not needing to open a browser.
Note if you delete a file from File Explorer, it will be deleted from both locations.
Syncing your document library: Sync SharePoint and Teams files with your computer (microsoft.com), Please also see https://support.microsoft.com/en-us/office/sync-sharepoint-and-teams-files-with-your-computer-6de9ede8-5b6e-4503-80b2-6190f3354a88#bkmk_change to stop the syncing of your fileschange the folders that sync for a site, or to stop syncing all files on a site.
Content-Type: Introduction to content types and content type publishing (microsoft.com)
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