A number of leading websites stopped working for a time on Tuesday, 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.
Affected websites displayed the message: “Error 503 Service Unavailable”.
Cloud computing provider Fastly, which underpins a lot of major websites, appeared to be behind the problems.
The firm said it was looking into issues with its global content delivery network (CDN) and was implementing a fix. Websites were also beginning to be restored.
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 are localised, so only affecting specific locations across Europe and the US.
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 is in the hands of a few companies, meaning when something goes wrong it causing 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.”
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 services, including Twitter’s emojis.