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OneDrive File Type Exclusions Control Synchronization for Sync Clients
Microsoft 365 message center notification MC597037 (updated June 27, 2023) brings news that the OneDrive sync client will display information about files blocked by synchronization by tenant administrators. Worldwide deployment of the updated sync client should finish by mid-July. In the past, users have been left in the dark when they discovered that some files wouldn’t synchronize, but now they can go to the Advanced settings section of the client to see what file types the tenant doesn’t allow them to synchronize.
Oddly, the description for Microsoft 365 roadmap item 124868 takes a different perspective and says:
“This feature will allow you to configure OneDrive Sync Setting to exclude selected files and selected file types from syncing to OneDrive. When available the configuration settings will be located in the OneDrive admin center.”
It seems like a little copy and pasting mistake because it’s long been possible for tenants to exclude file types from synchronization. Microsoft’s documentation explains how to achieve the goal using group policy. It’s also possible to impose a block by running the Set-SPOTenantSyncClientRestriction cmdlet from the SharePoint Online administration module. For example, this command blocks three file types:
Set-SPOTenantSyncClientRestriction -ExcludedFileExtensions "mp4;rar;zip"
TenantRestrictionEnabled : False
AllowedDomainList : {}
BlockMacSync : False
ExcludedFileExtensions : {mp4, rar, zip}
OptOutOfGrooveBlock : True
OptOutOfGrooveSoftBlock : True
DisableReportProblemDialog : False
Running the Set-SPOTenantSyncClientRestriction cmdlet is the same as blocking file types through the Settings section of the SharePoint Online admin center (Figure 1). Both update the same configuration, which the OneDrive for Business sync client downloads and applies when it synchronizes files from the user’s OneDrive for Business account and whatever SharePoint Online document libraries are synchronized locally.
The Effect of OneDrive File Type Exclusions on Synchronization
Introducing a block on a file type isn’t something to do without thinking. After I ran the cmdlet to block the MP4 file type, my OneDrive for Business client complained bitterly because it could no longer synchronize any Teams meeting recordings and other videos stored in OneDrive (Figure 2).
Teams meeting recordings are possibly a bad example. According to Microsoft, few people go back and view a meeting recording after it is made, which is the reason why Teams applies an expiration tag to recordings after creating the files in OneDrive for Business or SharePoint Online. But I have many other MP4 files for which I want to keep a local copy, so maybe MP4 shouldn’t be on the file exclusion list.
It took the OneDrive for Business sync client several days to recover after updating the SharePoint policy to allow the synchronization of MP4 files, but eventually everything settled down and the client is now happy to process MP4 files again.
OneDrive File Type Exclusions for Personal Sync Client
In any case, file exclusions for OneDrive for Business are old news. What’s new is that Microsoft allows OneDrive Personal users to set their own exclusion list in the latest version of the client (I am using version 23.124.0613.0001). Because the client is for personal use, there’s no system-provided values. Instead, it’s up to the user to input the set of file types they want to exclude through the Advanced Settings section of the client (Figure 3).
File type exclusions are specific to a device rather than an account. You’ll find the information you enter in the client in a text file at
c:\users\<user>\AppData\Local\Microsoft\OneDrive\settings\Personal>odignore.txt.
If you run OneDrive Personal on multiple workstations, you’ll need to configure the settings on all workstations.
OneDrive FIle Type Exclusions are Client-Specific and Don’t Affect the Browser
Th summary is that both the OneDrive for Business and OneDrive Personal sync clients now display details about file types excluded from synchronization. OneDrive for Business users can’t do anything to affect the set of excluded files (except persuade an administrator to change the tenant configuration) while OneDrive Personal users can make their own minds up. In both cases, remember that these settings only affect the OneDrive sync clients. They have no effect on the OneDrive browser client, meaning that users can upload and download whatever OneDrive content they like using a browser.
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