A9 (now sometimes referred to as A10) is the name of Amazon's product search algorithm. When a shopper types a query into Amazon's search bar, A9 determines which products rank, and in what order, from a catalog of hundreds of millions of listings.
Amazon's goal with A9 is straightforward: rank products that are most likely to result in a purchase. This differs from Google's algorithm, which optimizes for relevance and user experience — A9 optimizes primarily for revenue per search.
Core Ranking Factors
Relevance Signals
- Product title — the most heavily weighted text field
- Bullet points and description — parsed for keyword presence
- Backend search terms — hidden keywords entered in Seller Central
- ASIN attributes (size, color, material) — match structured browse attributes
Performance Signals
- Sales velocity — more recent sales = stronger signal
- Conversion rate (CVR) — listings that convert well rank higher
- Click-through rate (CTR) — products shoppers click on more earn ranking
- Session-to-purchase ratio — similar to CVR, tracked at the session level
- Price competitiveness — relative to category benchmarks
- Review count and rating — social proof correlates with conversion
External Signals (Indirect)
- PPC (Sponsored Products) — ads drive sales velocity which lifts organic rank
- External traffic — social media or email-driven traffic that converts
Why PPC Accelerates Organic Ranking
Running Sponsored Products campaigns on your target keywords generates sales that are attributed to those keywords. Amazon's algorithm registers the keyword → purchase link, which over time improves your organic position for those terms. This is the "halo effect" sellers use at launch to seed organic ranking.
What A9 Does Not Rank On
- Seller star rating (used for Buy Box, not search rank)
- Time in catalog (no "age of listing" bias)
- Number of images beyond threshold
Optimizing for A9
- Research high-volume, relevant keywords with low competition
- Place the most important keyword in the title (first 60 characters)
- Fill all five bullet points with secondary keywords and benefits
- Add up to 250 bytes of backend search terms (no repetition needed)
- Improve conversion rate through images, pricing, and reviews
- Use Sponsored Products to seed initial sales velocity on launch keywords