How Does Amazon’s A9 Algorithm Work?

Rick Wong 12 April 2021

What is Amazon A9 Algorithm?

The Amazon A9 algorithm is the algorithm that powers Amazon’s search engine. It allows Amazon to best match the customer searches to the customer’s desire product. It is one aspect, amongst many, that Amazon sellers would need to be aware of to become a successful seller.

What makes Amazon A9 algorithm unique is its emphasis on conversion or “purchases” that the customer has made. For example, if all things are equal on the search term “Garlic Press,” product A gets 40 conversions on this search term, while product B gets 30 conversions, product A should rank relatively higher than product B.

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Amazon’s A9 algorithm was very similar to Google’s search algorithm, with the key difference being sales conversions. Amazon is much more likely to promote listings that are more likely to result in sales. It will greatly value the following factors: product relevancy, sales history & conversation rate. If your product has a strong sales history and high relevancy to its search terms, it leads to high conversion rates. This makes it easy to maintain a high rank on the Amazon SERPs.

On the other hand, the Google search engine uses factors other than conversions. It uses the relevancy of the content measured by “bounce rates”. This reflects the nature of the two – Amazon is an E-Commerce “buying” website, and Google is a content discovery site. The key goal of Amazon is for the end customer to come out with a purchase of the product they are looking for. On Google, the goal is to have the user discover the right content.

Key Factors that Drives Amazon A9 Algorithm

Although Amazon has never stated the exact logic of the A9 algorithm. Based on my experience and other sellers we can deduce the key factors that drive ranking on A9.

Sales Velocity

The sales momentum of your ASIN, based on a moving average of a date range. This date range is highly speculative, but it is estimated to be around 30 days. That is why a lot of questions about ranking and sales momentum from the Amazon seller community. Also why it is hugely important to stay in stock.

Sales Rank

Sales Rank or Amazon Best Sellers Rank (BSR) is a number rank assigned to every single product in the Amazon product catalog once it’s had a sale. BSR is generally used to gauge how well a product is selling on Amazon in its category. BSR only applies to the category and sub-category of the product, not Amazon as a whole.

For example, you may very good sales and rank #5 seller in your category. Yet, that’s no indication of how well you’re doing on Amazon in its entirety. Thankfully, your rank on Amazon itself doesn’t matter, but your BSR in your subcategory or category definitely does. A customer will always trust a high-ranking product more than a lower-ranking one.

Amazon Best Sellers Rank Guide

Amazon is unclear on the actual calculations behind BSR. Based on research, most experts agree it involves 3 key factors. Product sales (both recent & historic), product price changes or promotions, and naturally, any competing products. While more weight is definitely put on recent sales, historical sales are taken into account. This means your BSR will not fluctuate too drastically as long as you have a good sales history.


There is a noticeable rank or algorithm boost due to the number of customer reviews you have on your ASIN. Although, there is a diminishing return as more reviews you collect. There is a bigger rank difference between a product with 0 vs. 100 reviews than 1000 vs. 2000 reviews. There are soon automation tools out there, such as FeedbackFive, that can automate the process of after-sales service on Amazon that can potentially up your review count.

Amazon Vine Program

In this program, selected ‘trusted’ reviewers on Amazon will receive your product for free in return for leaving a detailed and honest review. It is the best Amazon offered review program other than the Amazon Early Reviewer Program, which unfortunately ended in early March 2021.

Thankfully, the Vine Program is free to enroll in and takes just a click, as long as you meet the requirements.

The requirements of the Amazon Vine Program are:

  • You’re a brand registered seller
  • Your product listing has an image and description
  • You have available inventory for your product
  • Your product is in the ‘New’ condition
  • Your product is not a restricted or ‘adult’ product
  • You have less than 30 reviews on your product
  • You will bear the cost of any products you give away for free

Amazon’s Vine Program is the only legitimate way to gather reviews at the moment other than doing social media promotions. Please bear in mind that Vine Voice reviewers leave honest reviews, this does not mean they will leave a good review. Only enroll in the program if you’re confident your product is of a quality that meets your customer’s expectations.

Other than the Vine Program, there are other methods for gathering reviews such as offering rebates on RebateKey in exchange for reviews. However, this is not in line with Amazon’s TOS so we advise you to be careful in how you decide to gather your reviews.

Fulfillment Method

Amazon will give preference to products that are Fulfilled by Amazon (FBA) than not. This is centered around customer satisfaction, as FBA products are eligible for 1-2 days prime shipping. If you want to succeed in the Amazon game with a competition using FBA, enrolling in FBA is a must.

Amazon PPC

Using Amazon advertising and bidding on specific keywords, the A9 algorithm will give some organic rank to keywords that convert in a sale even if it is discovered by Sponsored Products. We have a comprehensive article on how organic rank can be achieved by just Amazon PPC here.

Off-Amazon Traffic

Driving quality traffic from Google and other social media such as Facebook will boost the A9 algorithm as well. Amazon indirectly has shown it has placed importance on off Amazon traffic by introducing Amazon Attribution.

Listing Optimisation

Having your listing optimized with relevant keywords placed in the right fields and with the right photography. Much more on listing optimization later.

The key to product relevancy is having a truly optimized and quality product listing. There are several ways to do this, but the main three are – having clear, attractive product photos, having descriptive titles, bullet points & product descriptions, and lastly, optimizing your listing with relevant backend search terms.

EBC or A+ Content

The best way to increase the attractiveness of your product listing is to use Enhanced Brand Content (EBC), also known as A+ Content.

Amazon A+ Content: Beginner's 'How-to' Guide | Sellics

As you can see above, the product description for this product- Hoover PowerDash Pet Carpet Cleaner contains a lot of useful images and descriptions. The product has its own banner, as well as smaller side images. This is what you call “enhanced brand content” on Amazon. Providing key product information to customers in a pleasing way that is not text-heavy is what leads a lot of Amazon customers to click ‘check-out.’

A+ Content is extremely easy to create, you don’t have to meet any specific requirements. Even new sellers can simply go to Amazon Seller Central -> Advertising -> A+ Content Manager and start making an EBC portfolio for their product.

It has an easy-to-use UI where you can attach images, and insert some text boxes. You can choose between a variety of designs and basic layouts as seen in the image below. It usually takes Amazon only 2-3 days maximum to approve your A+ content designs.

Amazon Combines Enhanced Brand Content and A+ Content for Sellers

Positive Feedback Loop “Flywheel Effect”

A lot of sellers are looking for that one tactic to be successful on Amazon. This pandemic of finding that one “magic pill” is exacerbated by Amazon gurus, influencers, and service providers looking to give the audience what they want.

Unfortunately, the truth is there not one tactic that allows you to be successful on Amazon for the long term. What needs to happen is that multiple positive effects need to work together. This in turn creates a positive feedback loop. This positive feedback loop allows the Amazon A9 Algorithm to get a full picture of whether your ASIN is really giving the customer what they want. Amazon has a term for this, and it is called the “Flywheel Effect.”

If the above steps on the flywheel do not work together in tandem, the positive feedback loop will stop. For example, if you concentrate on a tactic that gets you more clicks, but your conversion rate is bad relative to the competition, theA9 algorithm will not give you a net positive rank relative to your competition even though you have driven more clicks to your listing.

Keyword Research

It is very important to make sure that your product listing gets a positive impression from the Amazon A9 algorithm. You can do this by making sure you are using relevant keywords. Having relevant keywords in your product listing key areas such as title and bullet tells the A9 algorithm what exactly your product is. It’s also on your way to starting initiating the flywheel effect via impression given by your keywords.

Tools, such as Jungle Scout’s Keyword Tool allow you to perform keyword analysis on your competition, through a process called reverse ASIN. So what is reverse ASIN? It is a keyword gathering process where the software tool can take an ASIN and show keywords that customers used to search and purchase for that ASIN in the past.

Keyword Relevance

After you acquire a list of keywords via the reverse ASIN process, select a set of highly relevant keywords. You have to make sure that you eliminate the keywords that are relatively less relevant to each other. This step is not an exact science. This step is advantageous to native speakers of the marketplace they are selling for. It gives them an advantage over the Chinese sellers selling on these marketplaces.

You want a list of, at most, 30 keywords that are at least 80% relevant to the product. In other words, your ASIN should at least be 80% match with the keyword. What I am explaining to you is very subjective based on what you define as relevant. The number of actual keywords you can get in your reverse ASIN, or your product’s uniqueness.

How do you know a keyword is % relevant. The below example can be a broad guide for you to follow. If your product is a Yoga Wheel that is 10 inches in diameter in size, the following would be its keyword and related relevancy:

One quick and easy way to figure out relevancy is to do a search on Amazon using that keyword. See if the exact similar product is amongst both the Sponsored Ads and the first 5-6 organic results.

How to Optimize your product listing for Amazon A9 Algorithm?

The first step and probably the most important step is to have your product listing optimized. Time spent on optimizing product listings is time well spent. It will give you the most leverage on your listings. Having your product listing converting at 15% versus 20% is a huge difference. It will lower your cost per sale and hence increase your sales and profit materially.

We have written a very comprehensive guide on the topic of Amazon listing optimization. But we will also give a brief overview.


Titles should be within the 200 character limit, do not repeat words. Make sure to use one main keyword phrase at the beginning of the title. Then add information about the variation (size, color, model) right after. A good title format should look like the below.

{main keyword 1} – {variation} – {words in search term the describes product 1} – {words in search term the describes product 2….} – if it is an accessory to a main product add: “for {main product} – by {Brand}

Bullet Points

5 bullet points that can further expand on the benefits of the product. Try to speak to the audience. Add keywords into the bullet point if it makes sense. Make sure it makes grammatical sense when incorporating the keywords.

Product Description

The product description affects the A9 relatively less than the bullet points and titles. Feel free to describe and let the reader envision how using the product can relieve their pain point. Clarify potential questions about your product, such as is there a product warranty? what does the package include? Is anything the customer might need sold separately?

Backend Search Terms

Once you have optimized the front-end of your product listing- title, description, images, EBC – it’s time to optimize the backend.

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The backend search terms are on the backend of the listing and are not customer-facing. It is one of the data points picked up by the A9 algorithm is used to match customer searches. You will fill in the backend search term field within 249 bytes limit restrictions, excluding spaces or punctuation such as a comma. Below are some of the best practices for providing search terms:

  • Don’t include product identifiers such as brand names, product names, compatible product names, ASINs, UPC codes, etc.
  • Don’t provide inaccurate, misleading, or irrelevant information like the wrong product category, the wrong gender, out-of-context words, etc.
  • Avoid excessively long content. Respect the limits that are set for different fields.
  • Don’t provide redundant information already captured in other fields such as title, author, brand, etc. It won’t improve your product placement in shopping results.
  • When entering several words as a search term, put them in the most logical order. A customer is more likely to search for “big stuffed teddy bears” than for “teddy stuffed bears.”
  • Use a single space to separate keywords. No commas, semicolons, or carets are required.
  • Don’t include statements that are only temporarily true, such as, “new,” “on sale,” or “available now”
  • Avoid including subjective claims such as amazing, good quality, and so on, since most customers don’t use subjective terms in their queries
  • Don’t include common misspellings of the product name – our systems compensate for common customer misspellings and also offer corrective suggestions.
  • Don’t provide variants of spacing, punctuation, capitalization, and pluralization (“80GB” and “80 GB,” “computer” and “computers,” etc.) Our systems automatically include different case forms, word forms, and spelling variants for searching.
  • Don’t include terms that are abusive or offensive in nature.
  • Abbreviations, alternate names, topics, and key characters (for books, movies, etc) can be included as search terms.

If you’ve made a product listing on Amazon, then you have seen the Keywords section within the Advanced view. This section is absolutely ESSENTIAL to ranking higher on Amazon. Amazon allows you 250 characters within search terms. For beginners, you can use Reverse ASIN Lookup Tools like Helium10’s Cerebro to find products in your category from future/current competitors to find out what keywords they are ranking for.

cerebro reverse ASIN lookup - Harrison Bevins

Follow these simple steps to narrow down your search term volume:

  1. Focus on the first 3 organic searches, and sort results by high search volume and high relevancy, which in this case is the Cerebro IQ score
  2. Set a few basic filters e.g. a minimum search volume of 1000, a maximum rank of 20, and word count set to 2
  3. Export as an excel sheet, then filter by search volume in descending order, then filter by ranks, exclude any ‘null’ values, and sort it in ascending orders
  4. Grab the first 100 keywords, remove any duplicates, common words, phrases you want to remove, and convert it all to lowercase
  5. Remove any brand names and/or repetitive words from the search terms, then reduce it to 250 characters

After this, simply input it into your product listing’s search term box. You can also further enhance your listing by inputting the “Subject Matter”, and inserting more search terms in “Other Attributes”. For “Intended Use” and “Target Audience”, we recommend leaving it blank so it doesn’t limit your product to a smaller amount of searches.

Optimize Images

Make sure your main image is of high quality, very clear, and crisp with white background. Make sure your product takes up as much white in the background as possible, as you can make an impression on the thumbnail of the search results. Other photos you should have are product call out, instructional photos, and lifestyle photos.

Use Amazon Advertising to further Optimize

The Amazon in-platform paid advertising has a direct effect on the organic ranking of the product. This paid-to-organic traffic relationship is very different than other platforms. For example, on Google ads, if the customer searches and clicks on your Google ads, there is no direct effect on the organic ranking of that keyword.

On Amazon, the story is different. The factors that help influence Amazon’s organic ranking also influence Amazon’s paid search ranking. Meaning the goal of Amazon’s organic ranking algorithm is to serve products that are high on relevance and in buyability. You can read more detail on how Amazon PPC can influence Amazon’s organic ranking.

Another way to use Amazon PPC is to improve the optimization of your product listing by looking at the converting search terms’ metrics. The true litmus test on keyword relevancy is sales. With Amazon PPC, you can attribute keywords to their sale, giving a true read on the keywords’ relevancy.

So regularly look into your Amazon PPC campaigns’ reports, make sure that your listing has those keywords that have attributed to a sale. Continue to iterate this process to make sure your listing is as optimal as possible with the strongest keywords.

Amazon PPC is the key proponent to the success of most brands on Amazon in 2021. Due to the saturation of the Amazon marketplace, most of your competitors will already have quality listings, optimized search terms, and plenty of ratings. The information needed to succeed on Amazon is so accessible on the internet, that your competitors can do mimic what you do on all fronts except for one – the Amazon PPC bidding auction.

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Only 1-3 products can win that #1 sponsored ad rank, and the way to do it is to run effective ad campaigns using Amazon Advertising. We offer a multitude of resources on how to run ad campaigns, with comprehensive guides on ad campaigns, the key differences between types of campaigns, and even how to structure them and what campaign budgets to use. Once you have the campaigns up and running, it will be easier to measure your product’s performance on Amazon and rank it even higher.

Constant Analysis

The most valuable strategy to consistently rank your products higher on Amazon is “kaizen” or continuous improvement. Obtaining and then maintaining high product rank on Amazon needs constant analysis of different performance metrics, especially with active ad campaigns running. The best way to do this is to run Amazon PPC and then analyse the metrics within.

We recommend analysing the following key metrics for your products on a weekly basis, for month-over-month data:

  • Total Impressions – the number of times your ad was viewed by a customer
  • Total Clicks – the number of times your ad was clicked on by a customer
  • Bounce Rate – the rate at which a customer exits Amazon after clicking your ad
  • Total Spend – total spend of a keyword, ad type, or ad campaign
  • Total Sales – total sales from a keyword, ad type, or ad campaign
Amazon Seller Metrics to Track for Your Amazon Success

Some ratios that we recommend you analyze for high performing keywords for your products on a regular basis:

  • Clickthrough Rate (CTR) – the ratio of total clicks over total impressions
  • Conversion Rate (CVR) – the ratio of total conversions over total clicks, where conversions are clicks on ads that become sales
  • Cost Per Click (CPC) – the cost of a customer clicking on your ad, it varies according to auction so its good to look at the average CPC (aCPC)
  • Advertising Cost of Sale (ACoS) – the ratio of total ad spend over total sales

Generally, an ACoS below 30% for most keywords, and a high conversion rate of above 10% is ideal, and it will let your product rank consistently high. Still, these metrics vary a lot from seller to seller, so we recommend taking some Amazon PPC courses to fully understand them or instead of using the strategy in the next section of this article.

How SellerMetrics can help your listing optimize further for A9

As mentioned above, to get a stronger read on the relevancy of your keywords, you should regularly look into your Amazon PPC metrics. Ensuring you are 1) driving traffic from relevant keywords and 2) having these relevant keywords in your product listing will be very conducive to the Amazon A9 algorithm.

Our Amazon PPC Software, SellerMetrics, has an analytics feature that will allow you to see Search Terms and Keyword with their related metrics performance with just a few clicks of a button. You will no longer need to be running and downloading multiple reports and between multiple accounts on the Amazon advertising interface.

Use this feature to analyze your search term and keyword data by date range, then filter out your metrics (ACoS %, Orders, Sales etc) further by using the filtering dropdown.

The sort your filter Search Term/Keywords data by its orders/sales to find the top performers.

Our product’s beauty is our unified accounts feature, which consolidates all your Amazon accounts data into one screen. This unique feature, not offered by any of our competitors, will save time and optimize your analysis workflows. This is an amazing feature to have if you manage multiple accounts, such as Amazon PPC agencies.

A10 Algorithm

Amazon updated its A9 algorithm in 2020, leading to some interesting changes that altered seller’s ranking strategies.

Amazon A10 Algorithm Update: What's Important & What's Not - eStoreFactory

The A10 algorithm is very similar to the past algorithm. The only real difference is that it places less weight on PPC or sponsored links, and more on product relevancy. Amazon has always had a Consumer First mentality, so product relevancy is now the top priority. This does NOT mean that PPC is no longer useful! It is still integral to a successful Amazon business, especially in 2021… However, it does mean that listing optimization is now more important than ever.

If you have questions or insights to share, please feel free to post them via the comments section. Please also consider joining our Facebook Group where we discuss any questions you may have about running an Amazon business.

We are SellerMetrics, our Amazon PPC tool helps Amazon sellers, brands, KDP Authors and agencies navigate Amazon Advertising PPC via bid automation, manual bid changes, and analytics.




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