Thousands of websites have been disrupted after Amazon's huge cloud-computing service suffered a major outage.
Amazon Web Services, by far the world's largest provider of internet-based computing services, suffered an unspecified breakdown in its eastern US region.
It caused unprecedented and widespread performance problems for thousands of websites and apps.
While few services went down completely, thousands, if not tens of thousands, of companies had trouble with features ranging from file sharing to web feeds to loading any type of data from Amazon's "simple storage service", known as S3.
Amazon services began returning later and the company said on its service site that S3 was fully recovered and "operating normally".
The breakdown shows the risks of depending heavily on a few big companies for cloud computing. Amazon's service is significantly larger by revenue than any of its nearest rivals - Microsoft's Azure, Google's Cloud Platform and IBM, according to Forrester Research.
With so few large providers, any outage can have a disproportionate effect, but some analysts say the Amazon outage does not prove there's a problem with cloud computing - it just highlights how reliable the cloud normally is.
The outage, said analyst Dave Bartoletti, should not cause companies to assume "the cloud is dangerous".
Amazon's problems began when one S3 region based in Virginia began to experience what the company called "increased error rates".
Amazon S3 stores files and data for companies on remote servers. Amazon started offering it in 2006, and it is used for everything from building websites and apps to storing images, customer data and commercial transactions.
Major cloud-computing outages do not occur very often but they do happen. In 2015, Amazon's DynamoDB service, a cloud-based database, had problems that affected companies like Netflix and Medium. But usually providers have workarounds that can get things working again quickly.