When a website won’t load, many internet users turn to DownDetector, a site that keeps track of online disruptions, providing frequent updates on the status of the world’s digital infrastructure.

But the site, which calls itself the “weatherman of the digital world,” was no help on Tuesday when thousands of major websites showed the same so-called 502 error message for part of the morning. In a twist, DownDetector had also gone down.

The culprit was not a major technology company or a foreign government. It was a low-profile cloud-computing service, Cloudflare, which provides technological infrastructure for millions of websites, including Shopify, Dropbox and OKCupid.

The failure was a result of a software problem, Cloudflare’s chief technology officer, John Graham-Cumming, said in a statement on Tuesday. “This was not an attack (as some have speculated) and we are incredibly sorry that this incident occurred,” he wrote. He said the failure — the service’s second in two weeks — had lasted about 30 minutes.