Holiday retail sales jumped 3.4%, with online sales surging 18.8%, a faster e-commerce pace than last year.

About 8 in 10 consumers are expected to return at least one gift this year.

Post-holiday sales are also likely to boost consumer spending in 2019.

Americans opened their wallets extra wide this holiday, boosting retail sales 3.4% compared with a year earlier. Even more shoppers turned to online shopping, with e-commerce sales rising 18.8%, according to the latest spending data tracked by Mastercard.

Strong sales may continue after the holiday as Americans visit stores to make returns and hunt for post-Christmas bargains. Almost 8 in 10 consumers are expected to return at least one gift this year, according to online retail platform Oracle.

Amazon had a "record-breaking" holiday season, the company said in a statement on Thursday, declining to share many specifics. "Billions of items were ordered worldwide and tens of millions of Amazon Devices were purchased worldwide," the company said in a statement. It added that it gained about 5 million new Prime customers through trials or subscriptions this holiday season.

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In a nod to changing shopping habits, Amazon also expanded its return options this season, adding more free returns and increasing the number of locations where customers can drop off returns with no box or label needed.

President Donald Trump tweeted about U.S. holiday sales figures, calling it "the biggest number in U.S. history." However, on a percentage basis, 2019's sales increase is not the largest ever, given that retail holiday sales rose 5.1% in 2018, according to Mastercard data.

2019 HOLIDAY RETAIL SALES WERE UP 3.4% FROM LAST YEAR, THE BIGGEST NUMBER IN U.S. HISTORY. CONGRATULATIONS AMERICA! — Donald J. Trump (@realDonaldTrump) December 25, 2019

Post-holiday shopping is a growing part of America's retail action. Almost 70% of consumers say they're likely to shop in the week after Christmas, according to the National Retail Federation, with about half planning to take advantage of post-holiday sales and promotions. Even so, experts recommend that shoppers double check "deals" to make sure they really offer savings.

"Don't assume that a sale is a good deal," Julie Ramhold, senior staff writer at DealNews.com, a deal comparison website, told the Associated Press. "Do price comparisons."

Sites such as Camelcamelcamel.com, an Amazon price tracker, and Honey, a browser extension that tracks prices for major retailers, can help consumers figure out whether that sale is really worth it.

— With reporting by the Associated Press.