The figures apply across all online retailers for Amazon Prime Days. Tariffs and economic uncertainty are on the minds of shoppers as they prepare for Amazon's summer Prime Day sales. But at least one company is forecasting that sales for the online sales event will break records as budget-conscious shoppers look for deals.

Momentum Commerce, which manages online sales for 50 brands, said its Amazon purchases plunged 41% on Tuesday when compared with the start of Prime Day last year.

Retail analysts say the first day of Amazon’s Prime Day event and competing sales drove solid online spending.