The Amazon search algorithm determines which products customers see and which ones disappear into obscurity. Despite widespread speculation in the Amazon community, Amazon has never officially confirmed an A10 algorithm. The core of the system remains the A9 algorithm, even though it has been fundamentally overhauled and expanded over the years. Anyone serious about Amazon SEO must understand how A9 really works and which factors have the greatest impact on your ranking in 2026.
The Ranking Factor Hierarchy 2026
Based on extensive testing and analysis of hundreds of listings, the following ranking factor weighting emerges:
- Conversion rate: The single most important factor. Amazon wants to show products that customers buy. A conversion rate above the category average is the strongest ranking lever
- Sales velocity: The speed of sales, meaning how many units are sold per time period. High sales velocity signals to Amazon that the product is relevant and in demand
- External traffic: With 15 to 20 percent weighting, external traffic has reached unprecedented importance. In 2019, this factor had zero percent influence
- Reviews and ratings: For Rufus, Amazon's AI assistant, products need at least 4 stars to be recommended. Products below 4 stars are practically ignored by Rufus
- Seller authority: Your track record as a seller, including account health, delivery performance, and customer satisfaction
- Click-through rate (CTR): How often customers click on your listing when it appears in search results
- Listing quality: The completeness and relevance of your listing, including title, bullet points, A+ Content, and backend keywords
External Traffic: The Underestimated Ranking Booster
The weighting of external traffic has changed dramatically. From zero percent influence in 2019, the factor has risen to 15 to 20 percent weighting by 2025. Our tests show that just 5 to 10 percent external traffic share can lead to 20 to 30 percent higher organic rankings.
Why? Amazon interprets external traffic as a demand signal. When customers actively search for your product and come to Amazon through external channels, the algorithm treats this as a strong relevance signal. For tracking, use Amazon Attribution, which provides precise data on the performance of external traffic sources.
The most effective external traffic sources:
- Google Shopping Ads: Highly qualified traffic with clear purchase intent
- Social media (Instagram, TikTok): Particularly effective for lifestyle and consumer goods
- Influencer partnerships: Authentic recommendations with high conversion rates
- Email marketing: Your own customer lists for launches and promotions
Backend Search Terms: The 250-Byte Rule
Backend search terms are a frequently misunderstood ranking factor. The safest limit is 250 bytes (not characters). In the US, Amazon has expanded the limit to 2,500 characters, but for European marketplaces the more conservative limit still applies.
Critical to know: The byte limit works on an all-or-nothing basis. If you exceed the limit, ALL backend search terms are ignored, not just the excess ones. This is one of the most common and consequential SEO mistakes on Amazon.
Best practices for backend keywords:
- Do not repeat words already in the title or bullet points
- Do not use commas or semicolons, only spaces
- Include synonyms, regional terms, and common misspellings
- Do not include competitor brand names (policy violation)
Rufus: Amazon's AI Is Fundamentally Changing Search
Amazon's AI assistant Rufus is the biggest game changer for Amazon SEO in years. Rufus analyzes listings semantically and recommends products directly in search. The impact is massive: Rufus recommendations have only 22 percent overlap with traditional first-page results. This means Rufus often shows customers completely different products than the classic keyword search would.
The most important insight: Rufus exclusively recommends products with 4 or more stars. If your product sits below 4 stars, you are practically invisible to Rufus. This makes review management a direct SEO measure.
Keyword Research: Brand Analytics as a Goldmine
For keyword research, Brand Analytics with the Search Frequency Rank is the most valuable tool directly from Amazon. The Search Frequency Rank shows you the relative popularity of search terms on Amazon and is therefore significantly more meaningful than external tools that only provide estimates.
Our recommendation: Combine Brand Analytics with systematic competitor analyses. Identify the top 3 competitors for each of your keywords and analyze which factors drive their ranking: Is it price, review count, image quality, or A+ Content?
Conclusion: Amazon SEO Is a Holistic Concept
Amazon SEO in 2026 is more than keyword optimization. It is a holistic system of conversion optimization, external traffic, review management, and AI readiness. The A9 algorithm rewards listings that provide genuine value to customers and are optimized for Amazon's AI systems like Rufus.
For a professional Amazon SEO strategy, speak with our SEO agency team. Also read our detailed guide on Rufus optimization and the listing optimization guide.