Shoppers fought their way to the tills at UK retailers as the American tradition of Black Friday pre-Christmas discounting took firm hold here.
Many retailers traded from midnight to maximise shopping times and put deals online overnight.
But websites including John Lewis, Argos and Tesco Direct struggled to handle the increased traffic.
And Currys customers were left drumming their fingers as they waited up to an hour in a virtual queue.
At least online shoppers had only their own feelings of frustration to deal with.
During the day police were called to a number of disturbances at London and Manchester supermarkets as shoppers fought over goods.
There were reports of people pinching, punching and kicking to get to the bargains on offer.
John Lewis, which offered website deals from midnight, said that between midnight and 6am, traffic to johnlewis.com was up 307% compared with Black Friday last year.
John Lewis said its fastest selling product was the Apple iPad mini, while Nutribullet food processors were selling at a rate of one every 30 seconds.
But at the start of the day about 7% of its customers were unable to access the site first time due to the level of demand.
Currys PC World said it had seen its "biggest ever start" to Black Friday, with web traffic increasing fivefold from last year.
"Overnight we saw astonishing demand online and implemented a pre-planned queuing system to most fairly support shoppers," said Currys PC World e-commerce director Jeremy Fennell.
At midday, the queue to access Currys' website was over half an hour long.
Overnight, Tesco Direct also experienced high demand, and was temporarily unavailable.
As well as online, there was strong demand from shoppers in stores.
Asda said it sold more than 8,000 televisions in the first hour of trading, after its shops opened at 8am.
It had sold more than 1,000 BMX bikes by 9am, and had sold out of Microsoft XBox 360 250GB games consoles with Halo and Forza by the same time.
Asda's store in Wembley saw chaotic scenes as shoppers jostled for TVs.
An Asda spokesperson said: "We do not condone the behaviour of a very small number of people in our Wembley store this morning.
"Despite our extensive planning and additional security colleagues there was an isolated incident when the store opened. The sale has run smoothly in all our other 440 participating stores."
Later in the day online traffic jams had been resolved and shops were crowded but calm.
Despite the high volume of sales, some analysts cast doubt on the value of Black Friday promotions to retailers.
"All Black Friday is likely to do is bring forward business from December, reduce gross margins and undermine consumer's willingness to pay full-price again before Christmas," said retail analyst Nick Bubb.
"It is therefore good to see that Next are thinking long-term and preserving their pricing power," he added.
For decades Next has had two sales - one in the summer, and one at Christmas. The company is expecting a profit of between £750m and £790m for 2014, an increase of 8-14%.
Some US websites also experienced difficulties on Friday, including the website for electronics retailer Best Buy.
In the US, the Friday after the Thanksgiving holiday - Black Friday - has been the biggest shopping day of the year since 2001.
Consumers in the UK have been becoming more aware of the US tradition, and UK retailers have been investing in Black Friday promotions.
The number of visits to UK shops on Black Friday only really started to pick up last year, according to research firm Experian Footfall, rising 5.6%.