Tens of thousands of TalkTalk customers reported problems with their internet connection on Friday morning.
Popular tracking website DownDetector logged more than 30,000 reports beginning at around 10:00 BST, scattered across the UK.
TalkTalk’s Twitter feed was flooded with reports from users trying to work from home without internet.
The firm said the problem was fixed at around 11:30 BST, but it did not provide any details about the cause.
“We’re aware that some customers were unable to access certain websites for a short period earlier today,” the company said in a statement.
“The issue has now been resolved and we apologise for any inconvenience this may have caused.”
Earlier, it had suggested that some services were unaffected by the problem.
The scale of the failure is similar to one that struck Virgin Media a month ago, which caused intermittent problems until the following morning.
At the time, Virgin blamed the problem on “a technical fault in our core network”.