Keepa

Keepa tracks the price and sales rank history of products on Amazon. Its charts show how the Amazon price, third-party prices, Buy Box price and best sellers rank changed over months or years, and you can set alerts for when a price drops below a level you choose.

Resellers and private-label sellers read Keepa charts to judge how often a product actually sells, whether its price holds steady and how many sellers compete for the Buy Box. Brands use it to watch rival listings over time. A browser extension puts the chart directly on Amazon product pages.

Basic charts are free. Paid access adds more data, such as offer counts and rating history, plus product finders and a data API. Rank history is a proxy for sales, so learn how rank moves in your category before you draw conclusions from it.