How eBay’s Search Algorithm Cassini Works

For anyone selling on eBay, understanding how the platform’s search algorithm works is crucial to visibility and sales. Known as Cassini, eBay’s search engine determines which listings appear when buyers type in queries and in what order they are displayed. Much like Google or Amazon, Cassini is designed to surface the most relevant and trustworthy listings to maximise buyer satisfaction and conversions. For UK sellers competing in crowded categories, mastering Cassini can be the difference between steady sales and products getting buried pages deep in search results.

What Cassini Is

Cassini is the name given to eBay’s search engine algorithm. Launched in 2013, it replaced the previous search system with a more sophisticated approach focused on relevance, quality, and buyer behaviour. Cassini’s job is to connect buyers with the listings most likely to result in a purchase, taking into account a wide range of factors beyond simple keyword matching. This makes it more complex but also more rewarding for sellers who optimise correctly.

Why Cassini Matters to Sellers

Search is the gateway to sales on eBay. With millions of active listings in categories like electronics, fashion, and homeware, the majority of transactions begin with a search query. Cassini influences which products gain visibility and how often they appear in front of buyers. For UK sellers, where competition from international and domestic merchants is fierce, optimising for Cassini is vital. Strong performance in search increases traffic, sales velocity, and ultimately seller reputation, all of which feed back into the algorithm for even greater visibility.

How Cassini Works

Cassini evaluates listings across four core pillars: relevance, listing quality, seller performance, and buyer engagement. Relevance comes from how closely a listing matches a buyer’s query in terms of keywords and category. Listing quality refers to elements such as clear titles, detailed descriptions, high-quality images, and competitive pricing. Seller performance factors in reliability, feedback ratings, and fulfilment metrics. Finally, buyer engagement is measured through click-through rates, watchlist adds, and conversions. Cassini’s goal is to surface listings that both attract clicks and deliver a positive shopping experience.

Relevance and Keywords

Like any search engine, Cassini relies heavily on keywords. Sellers must use clear, descriptive titles that reflect how buyers search. For example, “Men’s Nike Air Max Trainers Size 10 UK Black” is more effective than a vague “Nike Shoes.” Item specifics and structured data also improve relevance, as Cassini uses filters to refine results. For UK sellers, using local spelling and sizing (such as “trainers” instead of “sneakers” or “size 10 UK” instead of US sizes) ensures alignment with buyer behaviour.

Listing Quality Signals

High-quality listings perform better in Cassini because they provide buyers with more confidence. Clear, high-resolution images, detailed item descriptions, and competitive pricing are all signals of quality. Offering free or low-cost shipping and including a generous returns policy also improves listing strength. Cassini rewards listings that look professional and trustworthy, as these are more likely to convert. For sellers in the UK, aligning with expectations shaped by platforms like Amazon Prime—such as fast delivery—can enhance perceived quality.

Seller Performance Factors

Cassini takes seller reputation into account when ranking listings. Positive feedback, low defect rates, and reliable dispatch all contribute to higher visibility. eBay’s Top Rated Seller status provides a significant advantage in search placement. For UK merchants, providing tracked shipping and quick handling times is especially important, as buyers have high service expectations. Poor performance, such as late deliveries or unresolved disputes, negatively impacts search rankings and overall visibility.

Buyer Engagement Metrics

Beyond keywords and listing quality, Cassini closely monitors how buyers interact with listings. High click-through rates signal that titles and images are compelling. Strong conversion rates show that listings are delivering on buyer expectations. Engagement through watchlists and repeat purchases also reinforces listing strength. Cassini uses this behavioural data to prioritise listings that demonstrate proven buyer appeal. This means that initial optimisation efforts are vital, but sustained performance depends on how buyers respond over time.

Best Practices for Optimising for Cassini

To succeed with Cassini, sellers should focus on creating clear, keyword-rich titles, completing item specifics, and writing detailed descriptions that answer buyer questions. High-quality images and mobile-friendly formatting are essential, as a large portion of UK buyers shop via smartphones. Competitive pricing strategies that include free delivery options can boost visibility, while strong customer service ensures positive feedback and repeat business. Regularly revising underperforming listings keeps them competitive and signals to Cassini that the seller is active and engaged.

Common Mistakes to Avoid

One of the biggest mistakes is keyword stuffing, which makes titles unreadable and reduces click-through rates. Another error is using stock images instead of original photos, which can harm both trust and SEO performance. Some sellers also neglect to fill in item specifics, meaning their listings are excluded from filtered searches. Ignoring mobile optimisation is a critical mistake, as poorly formatted listings drive away buyers. Finally, inconsistent shipping policies or long delivery times are major red flags for Cassini.

Performance Tips for Stronger Rankings

Sellers should test different title formats and monitor which keywords generate the highest engagement. Using eBay’s Terapeak research tool provides insights into trending searches and competitive pricing in the UK market. Running promotions such as multi-buy discounts can increase conversion rates, which Cassini rewards. Leveraging cross-selling through related items also boosts engagement. Tracking impressions, clicks, and conversion rates in eBay Seller Hub provides the data needed to continually refine and improve performance.

Future Outlook for Cassini

As ecommerce evolves, Cassini will continue to incorporate more advanced buyer behaviour signals and machine learning. Visual search, personalisation, and AI-driven recommendations are likely to shape how listings appear in future. For UK sellers, staying ahead will mean focusing not just on keywords but on building a strong brand presence within eBay. Sellers who consistently provide value, service, and transparency will be best positioned to thrive as the algorithm becomes even more customer-centric.

Conclusion

Cassini is more than just a search engine, it is the engine that powers visibility and sales on eBay. For UK sellers, understanding its focus on relevance, listing quality, seller performance, and buyer engagement is key to success. By optimising listings with the right keywords, strong images, competitive pricing, and excellent service, sellers can build momentum in search and outperform competitors. Mastering Cassini is not optional for eBay success—it is essential.