Google’s apps crash in a worldwide outage.

Internet users worldwide received a jarring reminder on Monday about just how reliant they were on Google, when the Silicon Valley giant suffered a major outage for about an hour, sending many of its most popular services offline.

At a time when more people than ever are working from home because of the pandemic, Google services including Calendar, Gmail, Hangouts, Maps, Meet and YouTube all crashed, halting productivity and sending angry users to Twitter to vent about the loss of services. Students struggled to sign into virtual classrooms.

As users scrambled to figure out what was going on, Google disclosed the outages on a status dashboard that shares information about its various services. Downdetector, a website for tracking internet outages, also showed that Google was offline. Google’s search engine continued to work for some people.

But about an hour after the outages began, the services started working again.

Google initially provided limited information about what occurred, and it was not immediately clear how many users were affected by the outage. Several of Google’s products have more than a billion global users, including Android, Chrome, Gmail, Google Drive, Google Maps, Google Play, Search and YouTube.

Later, the company attributed the problem to an “authentication system outage” that lasted for approximately 45 minutes ending at 7:32 a.m. Eastern time.

“All services are now restored,” Google said in a statement. “We apologize to everyone affected, and we will conduct a thorough follow up review to ensure this problem cannot recur in the future.”

Product outages were once fairly common for growing internet companies. But as Google, Facebook and others have become larger, building complex networks of interconnected data centers around the world, the incidents have become less common. Google has privately financed undersea cables to move data between continents and improve performance in the event problems occur in a certain location.

The reliability of the systems have become increasingly important as people and businesses depend on the services, whether to search for information online, find directions, send email or get access to private documents stored on Google’s servers. Some users reported their appliances not working because they were linked to Google’s line of home products.

During lockdowns, schools have leaned on Google services to teach students forced to stay home. “At least we have an excuse for not doing our homework,” one person wrote on Twitter.

The incident is likely to provide fodder for those who say the biggest technology companies have grown too powerful and deserve more oversight. In the United States, Google and Facebook are facing antitrust lawsuits. In the European Union, new regulations will be introduced on Tuesday to limit the industry’s power.

William Dixon, a cybersecurity expert at the World Economic Forum, said the outage highlighted the fragility of the world’s digital networks.

“What you have is an increasingly smaller number of technology providers that are systemically important,” said Mr. Dixon, who used to work on cybersecurity issues for the British government. “If there is one issue, then the cascades of that are quite significant.”