Chromium 141 Update Will Affect Offline Access for SharePoint Online and OneDrive for Business

Make Sure Policy is in Place to Maintain Offline Capability for Chromium 141-Based Browsers

The content of Microsoft 365 message center notifications often seems to assume that the reader understands the basic concepts underlying the news communicated in notifications. That’s not always the case. There’s so much change in the Microsoft 365 environment that few can track everything that happens and understand why a change is important.

MC1150662 is an example. This notification was originally published on 9 September 2025 and revised on 3 October 2025. It contains some important information and an action that tenant administrators should take before Microsoft rolls out an update as part of the deployment of Chromium 141 later this month. At least, I assume a further update is coming because the updates for Edge, Chrome, and Brave today all moved to Chromium version 141 (Figure 1) and the predicted issues have not emerged in any of those browsers.

Chromium 141 turns up in an Edge update. — Figure 1: Chromium 141 turns up in an Edge update

What Microsoft says will happen is that access to OneDrive for Business, Microsoft Lists, and SharePoint Online document libraries will be prompted to allow access to the local network (Figure 2).

A browser prompt for local network access after the Chromium 141 update (source: Microsoft). — Figure 2: A browser prompt for local network access after the Chromium 141 update (source: Microsoft)

Allowing access via the prompt controls the ability of OneDrive and SharePoint to use offline access to data and to use programs like Microsoft Nucleus, a synchronization engine for data-oriented information like Lists that’s also used by the Microsoft OneDrive Sync Service. Essentially, if access is not allowed, OneDrive synchronization and the intelligent incremental synchronization used by SharePoint Online will stop working.

That’s a pretty serious situation, but I’m not sure that people will realize this from MC1150662. Or maybe people are much smarter than I am, and I should stop worrying.

Updating the OneDrive Client

The easiest item on the must-do list is to make sure that workstations update to at least build 25.164 of the OneDrive sync client. The build number is revealed in the About page of the client settings (Figure 3).

Checking the version of the OneDrive sync client. — Figure 3: Checking the version of the OneDrive sync client

Updating Policies for Workstations

The next item is to deploy the LocalNetworkAccessAllowedForUrls policy to workstations with URL to allow the SharePoint Online and OneDrive for Business URLs to access local network endpoints (the workstation). The registry update file that I used to prepare Edge is:

[HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftEdgeLocalNetworkAccessAllowedForUrls]
"1"="https://office365itpros.sharepoint.com"
"2"=https://office365itpros-my.sharepoint.com

Figure 4 shows the update when applied to the system registry.

Updating the system registry with URLs for local network access. — Figure 4: Updating the system registry with URLs for local network access

See the Microsoft documentation for more details about how to apply the LocalNetworkAccessAllowedForUrls policy update for other browsers and for MacOS. One topic that isn’t covered in the documentation is if users with guest accounts need to update the system registry on their workstations to use B2B Sync to download files from SharePoint Online document libraries in host tenants, Without seeing the updated software in action, I assume that the change will require users to add the SharePoint endpoint for the tenants that they want to synchronize with to the registry. For example, if you have a guest account in the Contoso.com domain and want to synchronize files from a SharePoint Online document library that you have access to, you’ll need to include an entry for https://contoso.sharepoint.com.

Microsoft also recommends checking the values for the DisableNucleusSync and DIsableOfflineMode policies to make sure that their settings are as expected to allow users to work in offline mode with synchronized data.

Keep an Eye Out When Chromium 141 Arrives

It took me a while to get my head around the importance and impact of the information contained in MC1150662. The text above is my best interpretation of what Microsoft communicates in the notification. It’s hard to be definite until all the moving parts are available. Feel free to disagree!

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