By Georgia Wells and Robert McMillan
Computer systems at three of the world's largest technology companies went offline temporarily this week, thanks to an unusual and apparently coincidental series of glitches at Facebook Inc., Google and Apple Inc.
Facebook grappled with the most significant issues, blaming one of its longest-ever outages on a server-configuration error. The daylong outage that began Wednesday disrupted access to its core app, its photo-sharing app Instagram and its messaging service WhatsApp.
"Yesterday, as a result of a server configuration change, many people had trouble accessing our apps and services," Facebook said in a tweet Thursday. "We've now resolved the issues and our systems are recovering. We're very sorry for the inconvenience and appreciate everyone's patience."
A Facebook status page for developers had listed the outage as lasting 24 hours as of noon on the East Coast. An overnight message on Instagram's Twitter account had said the photo-sharing service was back running again, though some users reported lingering issues.
At Alphabet Inc.'s Google, some services, including Gmail, were slowed or outright inaccessible from Tuesday evening into early Wednesday on the East Coast. Google blamed a "cascading failure" that began after its engineers made tweaks to an internal storage service.
Separately, several of Apple's iCloud services were upended for more than four hours Thursday, according to the company's systems-status website.
While internet companies occasionally experience outages caused by problems ranging from natural disasters to surges of web traffic, it is rare for so many established companies to go down in one week and, in Facebook's case, to be disrupted for so long. The glitches knocked out a range of services -- email, messaging, social sharing, photos -- relied on by people around the globe.
"They're three really good, strong, technically innovative companies," said Christopher Brown, chief technical officer with Uptime Institute LLC, a company that provides consulting services on data-center reliability. "For them to have issues like this, it just goes to show how complex these systems are."
Facebook's disruption was significant not just in its length but its scope. The company has more than 1.5 billion daily users spread across its family of apps.
That size alone could be the culprit, said Jonathan Heiliger, a tech investor at Vertex Ventures who formerly was head of infrastructure at Facebook. As the company has moved to automate aspects of its tech, problems become more difficult to squash.
"Restarting the site: That is a big and complicated exercise that takes a lot more time than fixing the problem," Mr. Heiliger said.
The outage came as Facebook dealt with a different sort of disruption: the abrupt departure of a senior executive viewed as a potential successor to Chief Executive Mark Zuckerberg.
Facebook communicated little about the outage, except to say it wasn't related to a distributed denial-of-service attack, in which nefarious actors coordinate to bring down a service. Facebook hasn't publicly identified the cause of the outage. Its primary communications about the outage had taken place on Twitter.
The outage could force Facebook to issue refunds to advertisers -- many of which use its platforms as a core means of reaching consumers -- and further damage a brand already dented by scandals surrounding privacy and data protection. Even a one-day refund could sting: In its most recent quarter, Facebook logged $16.92 billion in revenue, or about $188 million a day.
At least one company benefited from Facebook's blip. Telegram Chief Executive Pavel Durov said in a public post that three million people signed up for the messaging company within 24 hours.
Rob Copeland contributed to this article.
Write to Georgia Wells at Georgia.Wells@wsj.com and Robert McMillan at Robert.Mcmillan@wsj.com