A major outage has affected a number of major websites including Amazon, Reddit and Twitch.
The UK government website – gov.uk – was also down as were the Financial Times, the Guardian and the New York Times.
Cloud computing provider Fastly, which underpins a lot of major websites, said it was behind the problems.
The firm said there were issues with its global content delivery network (CDN) and was implementing a fix.
In a statement, it said: “We identified a service configuration that triggered disruption across our POPs (points of presence) globally and have disabled that configuration.
“Our global network is coming back online.”
The issues began at around 11am BST and lasted for an hour. Other affected websites included CNN and streaming sites Twitch and Hulu. The outage also broke some parts of other services, including Twitter’s emojis.
Websites were also beginning to be restored, after around an hour of downtime.
Fastly runs what is known as an “edge cloud”, which is designed to speed up loading times for websites, as well as protect them from denial-of-service attacks and help them when traffic is peaking.
It currently looks as if the problems were localised, meaning specific locations across Europe and the US were affected.
Similar problems have affected Amazon Web Services, another huge cloud computing firm, in the past.
It has led some to question the wisdom of having so much internet infrastructure in the hands of a few companies, meaning when something goes wrong it causes mass disruption.
Jake Moore, a cyber-specialist at security firm ESET said: “this highlights the importance and significance of these vast hosting companies and what they represent.”
Adam Smith, a software testing expert with the BCS, the Chartered Institute for IT, said that outages with content delivery networks “highlight the growing ecosystem of complex and coupled components that are involved in delivering internet services”.
“Because of this, outages are increasingly hitting multiple sites and services at the same time.”