Microsoft is investigating a widespread outage that disrupted access to Microsoft 365 web applications and the Microsoft 365 admin center earlier today. The issue affected users attempting to connect to services like Outlook, OneDrive, and other Office 365 applications through their web browsers.
Outage Impact and User Reports
The outage, which began several hours ago, left affected users encountering error messages stating, “We’re experiencing a service outage. All of your open files have been saved. It may be some time before the outage is resolved.” Platforms such as Downdetector registered numerous complaints regarding connectivity issues across Microsoft’s web-based applications.
The problem was reportedly localized to specific users served through certain parts of Microsoft’s infrastructure. Desktop applications remained unaffected, and Microsoft advised users to shift to these, provided they had appropriate licenses as a temporary workaround.
We’re investigating an issue where some users may be unable to access Microsoft 365 apps for the web. We're reviewing service monitoring telemetry to isolate the root cause and develop a remediation plan. For more information, please refer to OO953223 in the admin center.
— Microsoft 365 Status (@MSFT365Status) December 10, 2024
Investigation of the Root Cause
Microsoft’s investigation focused on issues related to token generation within its authentication infrastructure. In a service alert, the company stated that it was also reviewing recent changes to identify the root cause of the incident.
“Impact is specific to some users, who are served through the affected infrastructure, attempting to access apps in Microsoft 365 for the web,” the company noted in its advisory.
Resolution Timeline
At 07:55 AM EST, Microsoft announced that it was testing a potential fix. The issue was traced to a token generation problem related to identifying token expiry times, which caused authentication requests to fail. To mitigate the disruption, Microsoft disabled proactive caching and deployed an alternate token generation flow.
By 08:18 AM EST, the company confirmed that the fix had been implemented and expected it to resolve the outage within approximately two hours. At 09:54 AM EST, after monitoring service telemetry, Microsoft declared the issue resolved.
We’ve confirmed after a period of monitoring that the issue is now resolved. For more information, please refer to OO953223 in the admin center.
— Microsoft 365 Status (@MSFT365Status) December 10, 2024
This isn’t the first time Microsoft has faced significant service disruptions. Just two weeks ago, a global Microsoft 365 outage affected services such as Microsoft Teams, Exchange Online, SharePoint Online, OneDrive, Purview, Copilot, and both web and desktop versions of Outlook. That incident, which lasted over 24 hours, led to delayed email deliveries and lingering issues with Outlook on the web.
Previously, in July, another major outage impacted services including Azure, the Microsoft 365 admin center, Intune, Entra, Power BI, and Power Platform. Microsoft later acknowledged that the nine-hour disruption was caused by a distributed denial-of-service (DDoS) attack compounded by an error in its DDoS protection mechanisms.
Following today’s incident, Microsoft has confirmed that the service has been fully restored after implementing a targeted fix and monitoring its systems for stability. Nonetheless, the recurrence of outages in recent months highlights the ongoing challenges faced by the tech giant in maintaining uninterrupted services for its global user base.
