Microsoft is investigating a widespread and ongoing outage affecting Microsoft 365, particularly Office web apps and the Microsoft 365 admin center.
Users impacted by the outage are seeing a message 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,” when attempting to access Microsoft 365 apps through a web browser.
According to a statement from Microsoft in an incident alert published in the admin center, the company is focusing its investigation on “token generation within our authentication infrastructure” and is reviewing recent changes to determine the root cause. The company added that the issue is affecting only certain users, specifically those served through the impacted infrastructure, when trying to access Microsoft 365 web apps.
As a temporary workaround, Microsoft recommends that affected users access their Microsoft 365 apps and documents through desktop applications, provided they have the necessary licenses.
At the moment, Microsoft’s service status, service health status, and Microsoft 365 network health status pages do not report any issues affecting the Microsoft 365 admin center, the company’s network, internet service providers, or customer network infrastructure.
This incident follows a similar worldwide Microsoft 365 outage two weeks ago, which impacted multiple services including Microsoft Teams, Exchange Online, SharePoint Online, OneDrive, Purview, Copilot, and both Outlook Web and Desktop. That issue was resolved after more than 24 hours, though Microsoft continued to address lingering problems with Outlook on the web and mail queuing delays.
In July, a massive outage affected multiple Azure and Microsoft 365 services, including the admin center, Intune, Entra, Power BI, and Power Platform services. The nine-hour outage was later traced to a distributed denial-of-service (DDoS) attack, which was amplified by an error in Microsoft’s DDoS protection mechanisms.
Update December 10, 07:55 EST: Microsoft is currently testing a potential fix to address the ongoing issues. The company identified a token generation issue that could be contributing to the disruption and is testing a fix to revert to an alternate token generation flow, which it believes will resolve the problem.
Update December 10, 08:18 EST: Microsoft deployed a fix expected to mitigate the outage within two hours. The company disabled proactive caching to alleviate some of the impact and believes that the fix will be completed within that timeframe.
Update December 10, 09:54 EST: Microsoft confirmed that the outage was caused by a recent service change that introduced an issue with identifying token expiration times, which led to authentication failures. The company has confirmed that the issue has now been resolved after monitoring service telemetry.