San Francisco: Dozens of major websites including Netflix, Uber and the BBC went down simultaneously in some areas of the US, but were soon up again in most cases.
The cause of the crashes remained unclear, but some appeared connected to trouble at a cloud service relied on by companies, although that did not stop the social media rumor and conspiracy mill from going into overdrive.
"We're aware that members are experiencing issues streaming on all devices," streaming television service Netflix said in a tweet at its customer service Twitter account.
"We're working to resolve the problem."
Netflix spokesman Joris Evers told AFP that the outage was the result of "technical issues" at an UltraDNS cloud service provided by Neustar and affected mostly US subscribers.
"UltraDNS is working to address the issue," Evers said. "We apologize for the inconvenience."
Neustar confirmed in a tweet that there was an issue with its UltraDNS.
Internet trouble tracker CurrentlyDown.Com displayed a list of two dozen websites that were or had been out of service during the day.
The list also included Ameritrade -- an online broker -- and The Economist.
It was unclear whether all those affected relied on UltraDNS, but ride-sharing service Uber blamed its problems on that.
The outages sparked chatter at Twitter and other social networks.
"Netflix, HBOGo, Chase Bank, Uber, ETrade... All websites down at the same time," tweeted Joseph Colarusso from the Twitter account @jcolarusso.
"Coincidence or Cyber Attack?"
The UltraDNS service was hit by an outage affecting customers in the eastern United States late afternoon local time, according to Neustar spokeswoman Lara Wyss.
"We can confirm this is not a DDoS attack," Wyss told AFP, referring to a style of cyber attack in which websites are intentionally overloaded with requests for service and crash under the stress.
Most of the websites that stumbled or fell were back up and running by mid-evening East Coast time, according to CurrentlyDown.
"Some of our clients experienced sporadic difficulty accessing some of our websites," Ameritrade told AFP.