Some early Prime Day results are in -- and retailers are seeing a bigger lift online than they did last year.

According to Adobe Analytics, which tracks data from 80 of the biggest 100 retailers in the U.S., said that large retailers -- defined by more than $1 billion in annual revenue, saw a 64% increase in online sales compared to a typical Monday. That surpasses last year's lift, which was 54% compared to an average day.  

Niche retailers, with less than $5 million in annual revenue, saw a 30% lift, Adobe said. Adobe typically releases its estimates for Amazon's Prime Day sales after the event is over.

Amazon (AMZN - Get Report)  itself doesn't release Prime Day sales figures, but tweeted on Tuesday that "predominantly small and medium-sized businesses" on its platform saw the largest amount of sales over a 24-hour period in Amazon's history. 

On the first day of #PrimeDay yesterday, worldwide sellers - predominantly small and medium-sized businesses - saw the biggest 24-hour sales day in Amazon history!

— (@amazon) July 16, 2019

Amazon's competitors, particularly major big-box retailers such as Target (TGT - Get Report) and Walmart (WMT - Get Report) , are increasingly cashing in on the mid-summer shopping bonanza.

"The bottom line is that for the big box retailers, there's upside for everyone," said Jerry Kurtz, head of retail at Infosys Consulting. 

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