Amazon.com's (AMZN - Get Report) hugely popular Prime Day will run for 48 hours this year, the online retailing giant announced on Tuesday, in a nod to both the Black Friday-like popularity of the annual event and Amazon's willingness to offer discounts to reel in and keep customers.

Amazon's fifth annual Prime Day will begin at midnight ET on Monday, July 15, the company said. While Amazon doesn't disclose revenue from its Prime Days, it did say that last year's shopping holiday was its "biggest global shopping event ever."

The company said the event will include more than a million deals around the world, including steep discounts on its own Alexa-enabled devices. Shoppers have to be Amazon Prime subscribers to take advantage of any deals.

Amid increased competition on both pricing and delivery options from the likes of Walmart (WMT - Get Report) and other big retailers, Amazon recently updated its Prime offering, expanding its free next-day delivery for more than 10 million products for Prime members.

This year's Prime Day will be the first in which free one-day shipping will be available to members with no minimum purchase amount.

Shares of Amazon were down slightly at $1,912.31 on Tuesday. Walmart also dipped to $111.13.

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