Amazon and eCommerce, in plain English.

Amazon SEO

Amazon SEO is the process of optimizing product listings to rank higher in Amazon search results and convert more shoppers into buyers. It covers keyword research (identifying the search terms shoppers use), title optimization, bullet point copy, product descriptions, backend search terms, A+ Content and review management.

Unlike Google SEO, Amazon SEO is primarily driven by sales performance — the more a product sells (especially at full price, without heavy discounting), the higher it tends to rank. This is why conversion rate optimization and pricing strategy are core parts of Amazon SEO, not just keyword placement.

Learn more: Amazon SEO & Listing Optimization Services

A10 Algorithm

"A10" is the name sellers and agencies commonly use for Amazon's current search ranking system, the successor to what was known as A9. Amazon does not publish an "A10" specification, so any list of ranking signals is based on observation rather than official documentation. Signals most practitioners watch are keyword relevance, click-through rate from search, conversion rate, sales velocity, reviews and ratings, stock availability, and traffic sent from outside Amazon.

Amazon has also published research on intent-based retrieval that goes beyond keyword matching. In practice that means consistent sales history and complete, specific listings matter, and lost momentum is harder to recover than to protect.

Learn more: How Amazon ranking works in 2026 · Amazon listing optimization

ACoS (Advertising Cost of Sale)

ACoS is the primary efficiency metric for Amazon PPC advertising. It expresses your ad spend as a percentage of the revenue those ads directly generated. Formula: ACoS = (Ad Spend ÷ Ad Revenue) × 100. If you spent $200 on ads and those ads generated $800 in sales, your ACoS is 25%.

Work out your own ACoS, TACoS and break-even ACoS with our free Amazon ACoS calculator.

A "good" ACoS depends entirely on your product's margin. If your net margin after COGS, FBA fees and other costs is 30%, an ACoS below 30% means you are profitable on ad spend. Most established sellers target a break-even ACoS or below. During a product launch, some sellers accept an ACoS above break-even for a defined period while reviews and sales history build; set that ceiling and end date before you start.

Learn more: Amazon PPC Management

ROAS (Return on Ad Spend)

ROAS is the inverse of ACoS — it expresses the revenue earned for each dollar (or pound) spent on advertising. Formula: ROAS = Ad Revenue ÷ Ad Spend. A ROAS of 4 means you earned $4 for every $1 spent on ads. ROAS = 1 ÷ (ACoS ÷ 100), so a 25% ACoS equals a 4x ROAS.

ROAS is more commonly used in Google Ads and Meta Ads contexts, while ACoS is the default metric on Amazon. Both measure the same thing from different angles.

Learn more: How to lower your Amazon ACoS · Amazon PPC management

FBA (Fulfillment by Amazon)

FBA is Amazon's logistics service. Sellers ship their inventory in bulk to Amazon fulfilment centres (warehouses), and Amazon handles storage, picking, packing, shipping, returns and customer service for every order. FBA products are eligible for Amazon Prime, which offers customers free next-day or two-day delivery.

FBA fees include a monthly storage fee (per cubic foot) and a per-unit fulfilment fee (based on size and weight tier). These fees make FBA less suitable for large, heavy or slow-moving products. The main advantages of FBA are Prime eligibility (which significantly boosts conversion rate), Amazon handling customer returns, and the "Fulfilled by Amazon" trust signal on product pages.

The alternative is FBM (Fulfillment by Merchant), where sellers ship directly to customers from their own warehouse or a 3PL. Learn more: Amazon Account Management