Thousands of users in Japan and China faced widespread access and sign-in disruptions to Microsoft 365 and Copilot services early Thursday, stemming from a critical routing issue in the company’s infrastructure.

Microsoft’s admin center status page confirmed the outage began around 12:00 AM UTC (8:00 AM JST / 8:00 AM CST), affecting a portion of service infrastructure handling traffic in Japan.

Users reported intermittent login failures, app loading errors, and degraded performance across core Microsoft 365 tools like Outlook, Teams, OneDrive, and the AI-powered Copilot assistant integrated into these platforms.

The incident, detailed in real-time updates, marks a rare regional disruption for Microsoft’s cloud ecosystem, which powers millions of enterprise workflows. Preliminary analysis indicates a routing misconfiguration that isolated healthy infrastructure, though Microsoft has ruled out cyberattacks in its initial statements.

We're investigating user reports of impact to Microsoft 365 Services and Microsoft Copilot in Japan. For more information, please see MO1198797 in the admin portal.
— Microsoft 365 Status (@MSFT365Status) December 18, 2025

By 7:40 AM GMT+5:30 (12:10 PM JST / 12:10 PM CST), Microsoft reported mitigating actions: engineers rebalanced traffic across redundant systems to restore availability. “We’re working to confirm full recovery,” the update noted, with the next status check promised within the hour—though a minor scheduling anomaly listed it for 7:04 AM GMT+5:30.

Earlier posts at 6:43 AM and 6:20 AM GMT+5:30 provided scope details, confirming impacts limited to the Asia-Pacific region without global spillover. No data loss or security breaches were reported, but the downtime disrupted business operations, remote work, and AI-driven productivity for affected organizations.

We’ve identified that a portion of service infrastructure that supports user traffic in Japan became unhealthy due to a traffic routing issue. We’ve taken mitigating actions to rebalance the traffic across healthy infrastructure to restore availability. Please see MO1198797 in…
— Microsoft 365 Status (@MSFT365Status) December 18, 2025

This follows a pattern of infrastructure hiccups for Microsoft, including a broader Azure outage in July that cascaded into 365 services.

Routing issues, often tied to BGP misconfigurations or peering problems, underscore the fragility of global cloud dependencies. Cybersecurity experts note such events can mimic DDoS attacks, prompting swift triage.

Microsoft urged users to monitor the admin center for updates. As of 7:48 AM IST, partial recovery signals were positive, but full normalization remains pending.

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