Amazon has said that a simple typo was the cause of several several high-profile websites and services being knocked offline earlier in the week.
Hours of problems struck services like Q&A forum Quora, and Giphy, an image hosting service.
The sites rely on hosting provided by Amazon Web Services (AWS) - a cloud computing provider.
A typo made during a routine debugging of the AWS billing system caused the failure.
"Unfortunately, one of the inputs to the command was entered incorrectly and a larger set of servers was removed than intended," Amazon said in an online statement.
The error required a full restart that "took longer than expected".
Around 150,000 websites and services rely on AWS.
Among those affected by the failure was - somewhat ironically - Down Detector, a service that tracks downtime at major websites.
Amazon, which is the world's largest provider of cloud services, says it is now making changes to help prevent a similar incident occurring in the future.