A massive internet outage has affected websites including the Guardian, the UK government’s website gov.uk, Amazon and Reddit. The issue made the sites inaccessible to many users for more than an hour on Tuesday morning. The outage was traced to a failure in a content delivery network (CDN) run by Fastly. It began at about 11am UK time, with visitors to a huge number of sites receiving error messages including, “Error 503 service unavailable” and a terse “connection failure”. Others affected included the publishers CNN, the New York Times, and the Financial Times, as well as the streaming services Twitch and Hulu. As well as bringing down some websites entirely, the failure also broke specific sections of other services, such as the servers for Twitter that host the social network’s emojis. The failure was not geographically universal. Users in some locations, such as Berlin, reported no problems, while others experienced massive failures across the internet. Outages were reported in locations as varied as London, Texas and New Zealand. Within minutes of the outage starting, Fastly, a cloud computing services provider, acknowledged that its content distribution network was the cause of the problem. The company runs an “edge cloud”, which is designed to speed up loading times for websites, protect them from denial-of-service attacks, and help them deal with bursts of traffic. The technology requires Fastly to sit between most of its clients and their users. That means that if the service suffers a catastrophic failure, it can prevent those companies from operating on the net at all. In an error message posted at 10.58 UK time, Fastly said: “We’re currently investigating potential impact to performance with our CDN services.” It was not until 11.57 UK time, almost an hour later, that Fastly declared the incident over. “The issue has been identified and a fix has been applied. Customers may experience increased origin load as global services return,” the company said in a status update. Despite speculation on social media that the outage was the result of a malicious attack, leading to the hashtag #cyberattack trending on Twitter, there is no evidence pointing to foul play. Instead, the company says a configuration error was at fault. A Fastly spokesperson said: “We identified a service configuration that triggered disruptions across our POPs [points of presence] globally and have disabled that configuration. Our global network is coming back online.” Boris Johnson’s spokesman said the government was aware of the problems with accessing gov.uk. He also said reports that users were unable to book Covid-19 tests online were being investigated as a “matter of urgency”. Asked if ministers believed a malicious foreign group or state was responsible, he said the outage “appears to be... affecting a number of sites globally, it doesn’t appear to be targeted at any one site”. Different websites handled the outage in different ways. The Guardian moved to Twitter to run a dedicated liveblog, while tech news site the Verge published news to a shared Google Doc – until a reporter accidentally shared a link on Twitter that allowed the audience to edit it. The increasing centralisation of internet infrastructure in the hands of a few large companies means that single points of failure can result in sweeping outages. In 2017, a problem at Amazon’s AWS hosting business, for instance, took out some of the world’s biggest websites for several hours across the entire US east coast. In 2020, a problem with Cloudflare, another CDN company, led to a half-hour outage for most of the internet in major cities across Europe and the Americas. The Cloudflare outage was eventually traced back to an error in a single physical link, connecting data centres in Newark and Chicago, that caused a cascading failure that knocked out almost 20 data centres worldwide.