correction

A headline on an earlier version of this report incorrectly said Amazon Web Services was down during the outage.

A massive outage struck large swaths of the Internet on Tuesday, causing the New York Times, Amazon, Hulu and other high-traffic websites to temporarily shut down.

The problem appeared related to the San Francisco cloud services provider Fastly, which many companies use to help their websites load faster. About an hour after the outages hit, the company said on its website it had identified a problem and applied a fix, allowing the affected sites to come back online. A Fastly spokesperson declined to elaborate.

The outage underscores just how important little-known Internet infrastructure companies like Fastly are to the normal functioning of the Web, and how even isolated disruptions can bring huge parts of online life to a halt. The pandemic-era shifts that sent more people to the Web for their groceries, work, school and health care have heightened the potential for broad shutdowns to cause real-world harm.

Even as the Internet grows, fewer companies are forming the backbone infrastructure that keeps all that traffic flowing to the right places. Existing companies tend to be the only ones able to handle the expanding workload, and smaller ones have trouble finding a foothold in the market, said Josh Chessman, an information technology analyst at Gartner.

“We’re seeing more and more being concentrated in fewer and fewer vendors,” he said. “Everybody has this perception of the Internet as this really robust thing, and it is, until it’s not.”

Other news outlets affected by the outage included CNN, the Guardian, Bloomberg News, the Financial Times and the Verge. High-traffic platforms such as Reddit, Pinterest and Twitch also were affected. The British government’s website was taken down, too, limiting access to public services, including the portal for booking a coronavirus test. Kentik, a company that helps businesses track Internet traffic, said Fastly suffered a global outage beginning at 5:49 a.m. Eastern time, which caused a 75 percent drop in traffic from its servers.

Similar outages have happened before. In July 2020, engineers at Cloudflare, which provides similar services to Fastly, accidentally pushed huge amounts of Internet traffic to a single data center in Atlanta, causing it to fail and take down websites like Medium and the video game League of Legends. In 2019, Verizon accidentally routed much of its U.S. traffic to a single Internet service provider in Pennsylvania, causing sites like Amazon and Facebook to stop working for many.

In the wake of high-profile ransomware attacks, such as the one against Colonial Pipeline in May or the meat processor JBS last week, concerns about the vulnerability of the Internet are rising.

Fastly runs a “content delivery network,” or a system of servers that its customers use to reduce the time it takes for their websites to load by storing larger files like images and videos closer to their end users. The 10-year-old company has a nearly $5 billion valuation.

Content delivery networks are particularly difficult to replicate because their business model requires having physical data centers spread across several countries. Fastly itself has more than 50. Larger cloud companies like Google or Amazon, which store the bulk of the Internet, have fewer, but larger data warehouses. Even Amazon has used Fastly to speed up the rate at which its pages load.

But content delivery networks aren’t the only point where glitches or hacks could cause widespread meltdowns. Website-hosting companies like GoDaddy, Squarespace and Shopify also are major choke points. Cloud giants like Amazon, Google and Microsoft rarely go down, but when they do, the effect is wide-ranging.

The importance of these companies means they are prime targets for hackers. They all spend large parts of their budgets on cybersecurity and extra redundancies to stop hack attacks and glitches, but they still happen from time to time.

“They’re targeted much more because of what they provide, but they also know that so they work harder to secure their systems,” Chessman said.

At the most basic level, the companies that control the physical pipes and wires of the Internet, like Verizon or AT&T, are also vital. When the Internet went down for hundreds of thousands of people on the East coast in January, a construction crew hitting a Verizon cable in Brooklyn was partly blamed.

Outages at content delivery networks and Internet service providers generally get resolved rapidly. Even so, the sheer amount of Internet traffic, and the reality that only a handful of companies provide these key services, means they are likely to keep happening.

“If the Internet were to truly go down, we would survive because we’re not 100% dependent on it,” Chessman said. “But it would be a major impact for society in general.”

Chris Alcantara contributed to this report.