KDSpy
Browser-based Amazon research overlay for category and sales-estimate style insights while you browse the store. Useful for quick competitive checks; always verify figures against your own sales data.
Ads & keyword research
Amazon keyword, category, and ads research tools used by working indie authors.
2 tools
Publisher Rocket
Amazon keyword and category research for authors: estimate demand, inspect competition, and build keyword lists for metadata and Amazon Ads. One of the best-known paid research tools in the indie space.