A9

A9 is Amazon’s proprietary search and ranking algorithm - the technology behind how product results are sorted and shown when a customer uses the search bar.

Although the name "A9" comes from “Algorithm” shortened (A + 9 letters), it also refers to the former Amazon subsidiary (A9.com) that originally developed the system.

A9 decides:

• Which listings appear for a given keyword
• In what order they appear (ranking)
• Which sponsored ads get shown in search results

It takes into account hundreds of factors, including:

• Relevance (title, bullet points, backend keywords)
• Performance (sales history, conversion rate, reviews, price)
• Customer behavior (clicks, purchases, bounce rates)
• Fulfillment method (FBA gets a boost)
• Availability (in-stock products rank better)
• Shipping speed and Prime eligibility

A9 is heavily commerce-driven: unlike Google, which emphasizes content quality, Amazon focuses on what listings are most likely to convert into sales.

Amazon has evolved past A9 into newer systems (sometimes called A10 by the seller community), but “A9” is still widely used as the general term for Amazon’s search and ranking engine.

Understanding how A9 works is crucial for SEO, PPC, and listing optimization.