User impact: Some users may be missing options to open files using custom file handlers in SharePoint Online 

More info: Custom file handlers enable users to open files with integrated third-party or line-of-business apps. For example, some users may have been missing the “Open in Adobe Acrobat” option for PDF files.

Final status: We’ve completed our rollback of the identified updates responsible for this impact and have confirmed through service-side testing as well as testing with previously affected users that this is mitigated. Due to cache storage, this can take up to 48 hours to resolve for all users. If users are in need of immediate remediation, please follow the articles below:

learn.microsoft.com/en-us/onedrive/developer/file-handlers/?view=odsp-graph-online&source=recommendations

learn.microsoft.com/en-us/onedrive/developer/file-handlers/reset-cache?view=odsp-graph-online

Scope of impact: Some users attempting to open files using custom file handlers in SharePoint Online may have been impacted. 

Start time: Sunday, March 29, 2026, at 11:00 PM UTC

End time: Wednesday, April 15, 2026, at 2:06 PM UTC

Root cause: A recent service update to SharePoint Online that changed how custom file handlers are resolved resulted in impact.

Next steps: 
– We’ll continue our review of the impacting update to better understand how the change resulted in impact and what we can do to improve our pre-deployment processes to identify and resolve similar issues.

This is the final update for the event.