Microsoft declared on Saturday that all services were fully restored, ending an outage that disrupted Microsoft 365, Outlook, Teams and the AI assistant Copilot across 74 countries and territories. The Redmond, Washington-based company said the failure stemmed from a technical issue during a network capacity upgrade, not from a cyberattack or artificial intelligence agents.

"We have completed our efforts to address the underlying issue of the incident and restored service to the remaining impacted customers and regions," Microsoft said in an update on X.

How far and how fast did the outage spread?

Problems first appeared around midday Thursday in the United States. Within one hour, the online tracker Downdetector had received outage reports from 74 countries and territories. The disruptions piled up across much of the world into Friday, with Outlook users unable to send or receive emails or load their inboxes.

The affected population sits in the hundreds of millions. Microsoft said on its website that over 430 million people use Microsoft 365 apps, and the company reported in January more than 450 million paid commercial subscriptions to the service. The total number of people affected by the outage remained unclear.

Microsoft said the incident "was introduced by an issue during an earlier network capacity upgrade that surfaced" following a recent network change. A series of posts by Microsoft 365 on X suggested engineers struggled for some time to bring the problem under control, drawing teasing from users and other companies. The company restored services gradually, which extended the timeline.

While fixing issues affecting Exchange Online mailboxes (Microsoft's cloud email service), the company earlier cited a failure that left a number of its servers "unexpectedly unavailable" during automated checks. Microsoft apologized on Friday and stated there was "no indication" of malicious activity behind the disruptions.

Which sectors were hit?

The outage reached governments, courts, healthcare services, businesses, airlines and banks. Governments in Japan, Singapore, Australia, Greece and Norway reported impacts on some operations, including email communications for certain ministries and agencies.

In Britain, the consequences were concrete:

• A criminal trial in Manchester was halted, and Judge Maurice Greene sent jurors home, saying the delays illustrated the danger of the court's reliance on technology.
• British police could not receive crime reports online and urged people to phone in urgent requests.
• The National Pharmacy Association warned of delays in getting medication, as the outage affected the National Health Service and threatened to prevent doctors from emailing prescriptions to pharmacies.
• The British government said it was "working closely" with Microsoft but that "robust contingency plans" were in place.

In the United States, the sheriff's office in Arapahoe County, Colorado, reported that online bond payments were affected. In Hong Kong, some banks saw disruptions, and businessperson Danny Lau, who runs an aluminum company, said his business could not receive updates from its U.S. customers through Outlook.

What does the outage reveal about concentration risk?

The disruptions offered the latest example of the cascading failures that can erupt when communications and technology platforms depend on a single provider. Some lawmakers outside the United States argued the episode shows the consequences of overreliance on American technology.

"With no emails coming or going, many office workers feel like they are having a virtual snow day," said Jeremy Singer, a professor at the University of Glasgow's School of Computing Science. He added: "This problem serves to emphasize the dependence we have built on one company's digital infrastructure, and may lead us to question whether we need more resilience in our IT ecosystem."

The ripple effects also reached the AI sector. OpenAI and Anthropic reported problems connecting with Microsoft 365 tools, underscoring how artificial intelligence platforms increasingly interact with other companies' software — and inherit their outages.