Some of the UK's biggest retailers are cashing in on a US tradition which sees millions of frenzied shoppers make the most of discounted prices.
In the US, thousands of stores discount their prices the day after Thanksgiving, and many open for longer hours.
Last year a record number of people visited stores over the Black Friday weekend, spending a total of $52bn (£32.6bn) - an average of around $400 (£250) each, according to the National Retail Federation.
And this year, some eager shoppers have been caught on camera phones battling to get to the best bargains first, after queuing for hours.
Many retailers opened their stores at midnight, and this year the trend to open at 8pm on Thursday started to spread.
While the shift was denounced by some store employees and traditionalists as pulling people away from families on Thanksgiving, many shoppers welcomed the chance to shop before midnight.
Online retailer Amazon was one of the first companies to bring the trend to the UK.
It launched a week-long Black Friday sale on Monday, which it claims "offers millions of pounds of savings on hundreds of Christmas gifts".
Tech giant Apple and Asda, owned by Walmart, are also hoping to make the most of the Christmas shopping rush by offering one-day discounts of their own.
Hotel Chocolat emailed customers to say that as it offered US customers 20% off it would do the same for UK buyers.
"There are more retailers launching sales this year than ever before - and many British consumers are becoming aware of the tradition for the first time," Retail Week's Gemma Goldfingle told Sky News.
"In the US it is an absolute phenomenon, with people queuing up all night to snap up the best deals."
"It has not reached that level here and whether it ever will is another matter," Ms Goldfingle said.
She (SNP: ^SHEY - news) said that Americans have Thanksgiving to kick-start the event – whereas in the UK it is just a normal day. Boxing Day, when UK sales traditionally begin, is a normal work day for Americans.
"A lot of British retailers would prefer not to have it," Ms Goldfingle said.
"They want to be selling items at full price ahead of Christmas, especially given the tough economic conditions."
While a limited number of UK chains have labelled their sales as Black Friday, many others have needed to show weekend price drops to lure customers.
Furniture chain dfs has taken to advertising in newspapers about its discounts while Topshop offered online weekend deals.
Black Friday, which is thought to refer to the first day of the year that retailers go "into the black", comes just ahead of Cyber Monday - which the marketing industry claims is the busiest day in the online shopping calendar.
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