For years, many Amazon sellers have been relying on the Keepa Chrome extension to track historical product sales data. It is the most popular Chrome extension because it gives such accurate information and also for the longest time it was free. As of February 2019, users now have to pay for access.

Keepa is great for getting a quick glimpse into how well products have been selling over time. But it does so much more than that. You can use it to get price drop and availability alerts. Set up a price watch directly from the product page. You can even import your Amazon Wish List.

When viewing products on Keepa or Amazon you will see:

• Extensive product details and average price
• Quickly view listing offers including historical prices
• Export all variation data of a product
• eBay New and Used price history

Find products matching any criteria by searching their entire product database. View the best selling products on Amazon by category. Lists are sorted by sales rank and updated daily. Browse Amazon's full category tree with deeplinks to corresponding best seller lists. View the top selling merchants on Amazon. You can then click on any seller in the list to view seller metrics and the storefront. By default the list is sorted by the number of ratings a merchant has.

Keepa also has a deal finder. Find products with the highest drop in price in your favorite product category on a daily basis.