How eBay’s Search Algorithm Cassini Works

At Lillian Purge, we specialise in Ecommerce SEO Services and have developed comprehensive guidance on How eBay’s search algorithm (Cassini) works.

eBay’s success depends on how efficiently it connects buyers with the most relevant products. That process is powered by its search engine, Cassini. Named after the famous NASA spacecraft, Cassini is designed to interpret user intent, surface high-quality listings, and reward sellers who create the best buyer experience. Understanding how this algorithm works is essential if you want your listings to appear higher in search results and ultimately sell more products.

This article explores what Cassini is, how it ranks listings, what factors influence visibility, and what sellers can do to optimise for it.

What is Cassini?

Cassini is eBay’s proprietary search engine, developed to replace the older Voyager algorithm. It powers every search made on the platform and determines which listings appear first when a buyer searches for a product. Unlike basic keyword matching, Cassini uses behavioural signals and performance data to decide which listings best satisfy the buyer’s intent.

It evaluates millions of data points in real time, considering relevance, conversion probability, and seller trust. Its goal is simple: ensure buyers find exactly what they’re looking for while rewarding sellers who deliver great service and accurate listings.

How Cassini Works

Cassini uses a multi-layered approach that combines keyword relevance, listing quality, buyer engagement, and seller performance. The algorithm doesn’t just match search terms it analyses how users interact with listings and which sellers create the most satisfying experiences.

Step 1: Query Understanding

When a buyer types in a search phrase, Cassini first interprets what they mean. It uses natural language processing and previous buyer behaviour to understand intent. For example, a search for “black trainers men size 10” signals both product type and specific attributes like colour and size. Cassini then filters listings that match these parameters.

Step 2: Relevance Filtering

Cassini evaluates the title, item specifics, and description to determine relevance. Keywords in the right places especially in the title and item specifics help listings qualify for inclusion in relevant searches. However, keyword stuffing harms visibility because the algorithm prioritises readability and relevance over raw keyword volume.

Step 3: Ranking and Sorting

After filtering for relevance, Cassini ranks listings based on performance metrics and buyer satisfaction signals. Factors include conversion rate, historical sales, shipping times, and customer feedback. Listings with better performance and consistent service tend to appear higher.

Step 4: Personalisation

Cassini personalises results using buyer data such as previous searches, watch lists, and purchase history. This means two buyers searching the same term may see slightly different results based on their preferences and past behaviour.

Key Ranking Factors in Cassini

Several core elements determine how Cassini ranks your listings. Optimising for these areas improves visibility and conversion potential.

1. Keyword Relevance

eBay relies heavily on keyword matching, so accurate titles and item specifics are vital. Titles should describe the product clearly, include key attributes like brand, model, and condition, and follow a logical structure. Item specifics (such as size, colour, and material) also help Cassini understand exactly what’s being sold.

2. Listing Quality Score

Cassini assigns an internal quality score based on how complete and detailed your listing is. Listings with high-resolution photos, accurate descriptions, competitive pricing, and clear return policies are favoured. eBay encourages sellers to use all available item specifics and avoid generic or incomplete listings.

3. Click-Through Rate (CTR)

When a buyer sees your listing and clicks it, Cassini records that interaction. A higher CTR indicates strong relevance, and Cassini uses this data to rank listings higher for similar future searches. Thumbnail quality, title clarity, and price positioning all affect CTR.

4. Conversion Rate

Cassini measures how often views turn into sales. Listings that consistently convert well are rewarded because they signal buyer satisfaction. If your product sells quickly after being viewed, Cassini interprets it as a strong match for buyer intent.

5. Seller Performance Metrics

Seller reliability directly affects visibility. Cassini rewards sellers with high feedback ratings, fast shipping, and low cancellation rates. Top Rated Sellers often gain a ranking advantage because eBay wants to promote trusted sellers that create positive experiences.

6. Customer Service and Returns

Offering free or flexible returns can increase visibility. Cassini prefers listings from sellers who resolve disputes quickly and provide responsive customer service. Positive buyer feedback plays a key role in building credibility within the algorithm.

7. Price Competitiveness

While not always decisive, price competitiveness affects CTR and conversion rates, both of which feed Cassini’s ranking model. Consistently overpriced items compared to similar listings may be ranked lower.

8. Listing Freshness

Regularly refreshing listings signals activity to Cassini. Outdated listings with long inactivity periods can drop in rankings. Revising titles, updating descriptions, or re-uploading photos can improve engagement and visibility.

How Buyer Behaviour Shapes Rankings

Cassini places strong emphasis on how buyers interact with listings. Every click, view, or purchase provides behavioural data that influences future results.

• High engagement: Listings that generate clicks, watches, or adds to cart gain authority.

• Bounce rate: If buyers click a listing but leave quickly, Cassini interprets it as irrelevant or low quality.

• Repeat interactions: When buyers save or return to listings, Cassini recognises these signals as positive engagement.

This behavioural approach makes Cassini dynamic. It continuously learns from user actions to refine future search results.

Common Mistakes That Hurt Cassini Rankings

Many eBay sellers struggle to understand why their listings are not appearing prominently in search results, even when using the right keywords. Cassini, eBay’s internal search engine, does not just rely on keywords to determine visibility. It also considers factors like listing quality, buyer engagement, pricing, and seller reputation. Understanding the most common mistakes that harm Cassini rankings can help you avoid them and improve your overall performance. Below are the key issues that often reduce listing visibility and how to fix them.

Using Poor or Misleading Titles

Your title is one of the most important elements of your eBay listing. Cassini analyses titles to determine how relevant they are to a buyer’s search query. A poor or misleading title can confuse both buyers and the algorithm, lowering your ranking in search results.

Many sellers make the mistake of keyword stuffing—adding too many unrelated or repetitive phrases in an attempt to rank for multiple searches. This not only looks unprofessional but can also trigger Cassini to demote your listing. Instead, focus on writing clear and accurate titles that describe what you are selling. Include relevant details such as brand, model, size, colour, and condition. For example, “Apple iPhone 13 Pro 128GB Graphite – Unlocked – Excellent Condition” performs much better than a vague or cluttered title like “New iPhone Great Deal Fast Shipping.”

Leaving Item Specifics Incomplete

Item specifics are the structured details that appear in the product listing, such as size, material, brand, colour, and compatible models. Cassini heavily relies on these fields to match listings with buyer searches. When item specifics are incomplete or missing, your listing is less likely to appear in filtered search results.

Buyers frequently use eBay’s filters to narrow down their choices. If your product lacks key details, it will be excluded from many of these filtered results, dramatically reducing visibility. Always fill in every relevant field when creating a listing. Even small details can improve your chances of being found.

Using Low-Quality Photos or Missing Images

Images are crucial for both buyers and Cassini. The algorithm prioritises listings with multiple high-quality photos that clearly show the product from different angles. Poor-quality images, blurry shots, or missing photos make your listings look less professional and trustworthy.

Cassini wants to promote listings that provide the best shopping experience. This means clear, well-lit photos on a neutral background that show product details accurately. If you sell clothing, for example, include close-up images of textures, tags, and any imperfections. Listings with professional-looking images tend to attract more clicks, which signals engagement to Cassini and helps improve rankings.

Overpricing Compared to Market Averages

Price competitiveness plays a major role in eBay’s search results. Cassini compares your prices with similar items across the platform. If your products are consistently priced higher than competitors without a clear reason, the algorithm is likely to reduce your visibility.

That doesn’t mean you always have to be the cheapest seller. Instead, ensure your pricing reflects your value. Offer better shipping options, include additional accessories, or highlight superior product conditions to justify a higher price. Regularly monitor competitor listings to stay aware of market trends and adjust your pricing strategy accordingly.

Ignoring Feedback and Seller Performance

Cassini takes seller reputation very seriously. Negative feedback, unresolved disputes, or frequent late deliveries can all hurt your rankings. eBay’s search engine rewards sellers who consistently deliver great customer experiences.

If your account accumulates poor feedback or late shipments, Cassini sees it as a risk to buyer satisfaction. Focus on maintaining a high feedback score by communicating with buyers promptly, dispatching items quickly, and resolving any issues professionally. Consider offering free returns or guarantees to build trust and encourage positive reviews.

Vague or Misleading Descriptions Leading to High Bounce Rates

Bounce rate is another key performance indicator that Cassini monitors. If buyers click on your listing but quickly leave without taking action, it signals that your listing did not meet their expectations. This often happens when descriptions are vague, incomplete, or misleading.

Be honest and detailed in your product descriptions. Include accurate information about the condition, measurements, materials, and features. If the product has flaws, mention them clearly and include photos. Buyers appreciate transparency, and it leads to lower return rates and higher satisfaction scores. Use bullet points or short paragraphs to make descriptions easy to read, and include relevant keywords naturally rather than forcing them.

Not Optimising for Engagement and Mobile Users

Most eBay traffic now comes from mobile devices, and Cassini rewards listings that are mobile-friendly. If your description is poorly formatted or cluttered with unnecessary text or HTML, it may display badly on smaller screens, discouraging engagement.

Keep your listing layout clean and responsive. Make sure your titles, photos, and call-to-action buttons appear clearly on both desktop and mobile. Encouraging buyers to watch or save your listing can also signal strong engagement to Cassini.

How to Recover from Poor Rankings

If you suspect your listings are being suppressed or underperforming, start by analysing your performance in eBay’s Seller Hub. Review traffic data, impressions, and conversion rates to identify where the problem lies. Update weak titles, complete missing item specifics, and replace poor-quality images.

Also, focus on improving your overall seller metrics, including on-time shipping and customer satisfaction. Refreshing older listings and running limited-time promotions can help boost engagement and visibility.

How to Optimise for Cassini

Optimising for Cassini, eBay’s powerful search engine, is about more than just adding keywords. It involves combining solid SEO techniques with excellent customer service, engaging content, and ongoing data analysis. Cassini is designed to reward listings that create the best experience for buyers—those that are accurate, detailed, and trustworthy. To rank higher in search results and attract more sales, sellers need to understand what Cassini values most. Here’s how to fine-tune your eBay listings for maximum visibility and performance.

Craft Precise and Readable Titles

Your title is the first thing both Cassini and potential buyers will notice. It must be clear, descriptive, and easy to read. Cassini looks for natural keyword placement rather than forced or repetitive phrasing. For example, “Nike Air Max 270 Trainers Black Men’s Size 10” is informative, specific, and structured in a way that mirrors how buyers search. Avoid unnecessary words such as “amazing,” “cheap,” or “free shipping,” as they add little value to search relevance.

When writing titles, include the most important details: brand, model, product type, colour, and size. Keep within eBay’s 80-character limit but make every word count. Buyers are more likely to click listings that immediately tell them exactly what they’re looking for.

Use Complete and Accurate Item Specifics

Item specifics are critical for Cassini’s indexing process. These are the structured data points—like brand, size, material, and model—that help eBay categorise and filter products. The more complete your item specifics are, the easier it is for Cassini to match your listing to a buyer’s search.

Fill in every field available, even the optional ones. For example, a clothing listing should include size, fit, fabric, and pattern, while an electronics listing might include model number, storage capacity, and connectivity options. These details not only improve search rankings but also make your listing appear in filtered results when buyers narrow down their searches.

Using accurate item specifics also helps build buyer trust. Shoppers want to feel confident they’re purchasing the exact product they need, and detailed specifics reduce the risk of returns or complaints later.

Write Detailed and Informative Descriptions

Your description provides the opportunity to expand on your title and item specifics. This is where you can showcase your product and convince buyers to complete a purchase. A strong description includes relevant details such as condition, features, dimensions, materials, and compatibility.

Avoid keyword stuffing or copying manufacturer descriptions directly, as this can make your listing appear spammy or unoriginal. Instead, write naturally while using keywords sparingly and contextually. For example, if you’re selling a vintage camera, mention “vintage Canon AE-1 film camera with 50mm lens” once or twice in your text, but focus on describing its working condition, visual appeal, and included accessories.

Formatting also matters. Break up long blocks of text into short paragraphs or bullet points for readability. A well-organised description keeps buyers engaged and signals professionalism to Cassini.

Upload High-Quality and Relevant Images

Images are one of the strongest ranking factors in Cassini’s algorithm because they directly impact buyer engagement. Listings with multiple high-quality photos receive more clicks, longer view times, and higher conversion rates. Cassini recognises these signals and ranks such listings higher.

Use clear, well-lit images that show the product from multiple angles. Avoid blurry or pixelated pictures, and use a plain, neutral background to keep the focus on the item. Include close-ups of any important features, details, or imperfections so buyers know exactly what they’re purchasing.

If possible, use all available image slots to maximise visual appeal. Remember that your first image is the thumbnail that appears in search results, so make sure it stands out and accurately represents the product.

Encourage Positive Feedback and Great Customer Service

Cassini rewards sellers who provide excellent customer experiences. Positive feedback, fast dispatch times, and professional communication all contribute to higher rankings. Negative feedback, delayed deliveries, and unresponsive behaviour can have the opposite effect, lowering visibility.

To maintain a strong reputation, ensure your listings are accurate, pack items securely, and ship promptly. Respond to buyer queries quickly and politely, and resolve disputes professionally. If issues arise, offer solutions such as returns or exchanges to maintain goodwill. Consistent five-star ratings and satisfied customers are key to building long-term trust with both buyers and Cassini.

Review Performance Data and Refine Listings

eBay’s Seller Hub is an invaluable resource for tracking your listing performance. It provides detailed metrics such as impressions, clicks, conversion rates, and sales data. Regularly reviewing these insights helps you understand what’s working and what needs improvement.

If you notice certain listings have high impressions but low conversions, the issue could be your pricing, images, or descriptions. Alternatively, if impressions are low, your keywords or item specifics may need optimisation. Use these insights to make data-driven adjustments to titles, prices, or categories. Over time, consistent monitoring and small refinements lead to steady growth in both visibility and sales.

Stay Active and Keep Listings Fresh

Cassini favours active sellers who regularly update and manage their listings. Stale or inactive listings can slowly lose ranking positions over time. To stay relevant, revise listings periodically by updating keywords, refreshing images, and adjusting prices based on current market trends.

If you have a large inventory, rotate featured products or run limited-time promotions to encourage engagement. Frequent updates signal to Cassini that your store is active and responsive to buyer needs. The more engagement your listings generate through views, bids, or purchases, the stronger their visibility becomes in search results.

Maintain Consistency Across All Listings

Cassini also values consistency in listing quality and customer experience. Make sure all your listings meet the same high standard for titles, descriptions, and images. This helps build brand recognition and ensures that every product reflects your professionalism. Consistency also improves user trust, which increases repeat business and positive feedback—two factors Cassini considers when ranking sellers.

The Role of External Traffic

Cassini doesn’t operate in isolation. External traffic visitors from Google, social media, or advertising also impacts ranking. Listings that attract steady external clicks and conversions can receive a visibility boost because they demonstrate strong demand.

Sellers can leverage external marketing strategies such as Google Shopping ads, email campaigns, or social media promotions to drive targeted traffic back to their listings. This not only increases sales but strengthens Cassini’s perception of relevance and popularity.

Challenges with Cassini

Cassini’s complexity can make it difficult for sellers to fully understand why certain listings perform better than others. eBay doesn’t disclose its exact ranking formula, and updates are rolled out quietly. This opacity means optimisation is an ongoing process of testing, analysing, and refining.

Additionally, competition on eBay is fierce. Two similar listings may differ only slightly in price or feedback, yet one might rank significantly higher. Small details such as shipping speed or description quality can make the difference between appearing on the first page or being buried deep in results.

Cassini and the Future of eBay Search

eBay continues to evolve Cassini with advances in machine learning and AI. The platform is moving towards predictive personalisation, where search results adapt to each buyer’s behaviour, purchase history, and preferences in real time.

Future updates may integrate visual search, voice search, and deeper contextual understanding to improve relevance even further. Sellers who prioritise data-driven optimisation, excellent service, and transparent listings will remain best positioned to succeed under these evolving conditions.

Advice for eBay Sellers

• Prioritise buyer satisfaction above all else. Cassini’s ultimate goal is to deliver the best experience for buyers, so every metric connects to that outcome.

• Track key performance metrics weekly. Identify drops in impressions or clicks and adjust titles, photos, or pricing accordingly.

• Use eBay Promoted Listings sparingly and strategically. Paid promotion can boost exposure temporarily, but organic ranking improvements deliver longer-term stability.

• Combine on-platform optimisation with off-platform visibility. SEO for your eBay listings and brand awareness through social channels reinforce each other.

Conclusion

Cassini is one of the most sophisticated search algorithms in eCommerce. It goes beyond simple keyword matching to evaluate user intent, behaviour, and satisfaction. Sellers who invest time in understanding its mechanics gain a clear competitive advantage.

By optimising titles, improving customer experience, and analysing engagement metrics, you can strengthen your listings’ visibility and conversion rates. Cassini rewards precision, performance, and professionalism, so mastering these principles ensures lasting success on eBay.

We have also written in depth articles on eBay vs Amazon: key differences sellers need to know and How shipping times impact your eBay search visibility as well as our eBay Hub to give you further guidance.