Amazon reveals the best-selling items that it says helped Cyber Monday become its biggest sales day in history

• Amazon announced on Tuesday that Cyber Monday has once again become the company's single biggest sales day in history.
• It also revealed the items that customers purchased the most.
• Some have speculated that Cyber Monday might be losing strength due to online shopping growing on the other days that come before it, like Black Friday and Thanksgiving.

Amazon announced on Tuesday that Cyber Monday has once again become Amazon's single biggest shopping day in history. This follows a pattern for the e-commerce giant, as Amazon's previous biggest day for shopping was Cyber Monday in 2017.

"Black Friday and Cyber Monday continue to break records on Amazon year over year, which tells us that customers love shopping for deals to kick off the holiday shopping season," Jeff Wilke, CEO of Amazon's worldwide consumer business, said in a statement.

Read more: Thanksgiving is killing Black Friday by replacing it

Amazon also revealed the best-selling items on Amazon.com on Cyber Monday. Top movers included the Echo Dot, which is frequently discounted to half price or more on holidays like Black Friday or Prime Day. The best-selling items also included the AncestryDNA kit, Bose QuietComfort 25 noise-cancelling headphones, Michelle Obama's new book "Becoming," the classic game Jenga, and the six-quart version of the Instant Pot.

Some experts have questioned how long Cyber Monday can go on as its own event. This Black Friday, online sales came in just shy of last year's Cyber Monday total of $6.6 billion with $6.2 billion for the day, according to Adobe Analytics.

The latest shopping trends challenge the idea of Black Friday as the day for in-store shopping and Cyber Monday as the time for online shopping. Customers don't necessarily look at it that way anymore.

"Significantly early reports of buyer intent shows that 33 percent of US shoppers will mostly or only shop Black Friday online, taking away from some of the Cyber Monday uniqueness," Ray Wimer, an assistant professor of retail practice at Syracuse University, said in an email before Black Friday.

Cyber Monday pulled in an estimated $7.9 billion in online sales, good for about 19% growth over last year, according to Adobe Analytics. It's still a record, but doesn't match the pace of growth seen on Thanksgiving (28%) and Black Friday (23.6%) this year.

Here's the list of Amazon's Cyber Monday best sellers: