KDSpy

KDSpy is a browser extension that surfaces market intelligence the moment you click its button on any Amazon search results page. Instead of copying ASINs into a separate app, you see sales estimates, revenue projections, and category competition data overlaid on Amazon itself — making it the fastest way to validate a niche idea or benchmark a competitor.

What You Get#

• Sales & Revenue Estimates: Monthly sales and income projections for any book in Amazon's catalog, drawn from BSR data across Kindle, paperback, and hardcover formats.
• Category Intelligence: Analysis of 25,000+ Amazon categories — click any category to see average sales, competition levels, and the daily sales needed to reach the top 20 or earn a #1 bestseller rank.
• Author & Publisher Analysis: Investigate competitor author pages to see catalog performance and pricing strategies without navigating multiple pages manually.
• 30-Day Sales Tracking: Monitor a book's sales rank and revenue trajectory over a month — useful for tracking your own launch or watching a competitor react to price changes.
• AI Niche Insights: ChatGPT-powered prompts that analyze a niche's viability and surface keyword angles that manual browsing might miss.
• International Coverage: Research across 13 Amazon stores — US, UK, Canada, Germany, Australia, Italy, Spain, France, India, Japan, Mexico, Brazil, and Poland.

Who It's For#

• Niche validators: Authors testing whether a genre or topic has enough demand before writing. KDSpy's browser-based speed makes it ideal for rapid idea screening across multiple categories.
• Category strategists: Authors who want to identify the least-competitive subcategory where their book can realistically earn a #1 bestseller tag.
• Budget-conscious researchers: At $79 one-time versus Publisher Rocket's $199, KDSpy suits authors who want solid market intelligence without the premium price.

Pricing: One-time $79 — no subscription, no renewal. Includes a dual license for two devices, lifetime updates, and a 60-day money-back guarantee. Works on Chrome, Firefox, Edge, Opera, and Brave; Windows, Mac, Chromebook, and Linux.

Strengths#

• No app switching: Market data appears directly on Amazon search pages without leaving the browser — the workflow advantage over desktop apps is real.
• Category depth: Access to 25,000+ Amazon categories is broader than most competitors; finding the right subcategory for a bestseller ranking is easier here than anywhere else at this price.
• One-time pricing: Permanent access at less than half of Publisher Rocket's cost is a meaningful advantage for authors who need basic market research without advanced ad keyword tools.

Limitations#

• No keyword search volume: KDSpy does not show estimated monthly search volume for keywords — a critical gap compared to Publisher Rocket. You can validate category demand, but you cannot evaluate which search terms drive that demand.
• No Amazon Ads support: No AMS or Sponsored Products keyword research. Authors running paid advertising campaigns need Publisher Rocket or Helium 10 for that function.
• Dated interface: Multiple reviews from 2024–2025 note the UI looks outdated — functional, but not polished. The core research workflow is unchanged since early versions.
• No Safari support: macOS users who prefer Safari must switch to Chrome, Firefox, or Edge to use the extension.

Alternatives#

Publisher Rocket ($199 one-time) adds keyword search volume, competition scores, and AMS ad keywords — making it more complete for launch planning and paid advertising. Many experienced authors use both: KDSpy for quick category and sales validation during research, Publisher Rocket for keyword strategy when preparing to publish or run ads.