The eBay Cassini algorithm is eBay’s proprietary search and ranking engine that determines the order in which listings appear in eBay search results for any given buyer query. Cassini evaluates every active listing against more than 30 signals to produce a relevance and quality score. The highest-scoring listings appear at the top of the default Best Match search results. The signals Cassini evaluates include keyword match between search query and listing title, seller performance level, price competitiveness relative to similar sold listings, listing engagement rate, shipping terms, return policy, item specifics completeness, and Promoted Listings status. Understanding Cassini’s ranking factors allows sellers to optimize their listings for maximum visibility without additional advertising spend.
Cassini is defined as eBay’s search relevance and ranking algorithm that functions as the decision engine between buyer search queries and seller listings. Cassini matches buyer intent (what the buyer typed and filtered for) to seller supply (what the seller listed and described) using a multi-signal scoring model. eBay deployed the Cassini algorithm in 2013, replacing the earlier search system that ranked primarily by listing end date.
What Is the eBay Cassini Algorithm and What Signals Does It Use?
eBay Cassini uses more than 30 ranking signals grouped into 4 categories: relevance (keyword match, category, item specifics), seller quality (performance level, feedback score, defect rate), listing quality (price, shipping terms, return policy, engagement metrics), and buyer intent signals (buyer’s search history, location, filter preferences). No single signal dominates; Cassini weights all signals simultaneously to produce a relevance score per listing per search.
Relevance signals are the most immediately impactful signals sellers can control. A listing whose title contains every word in the buyer’s search query scores higher on relevance than a listing whose title contains only some search terms. Item specifics (Brand, Model, Condition, Size) that match the buyer’s filters boost relevance scores for buyers who use filter tools.
Seller quality signals reflect the seller’s history of delivering reliable transactions. A Top-Rated Seller ranks higher than an Above Standard seller, all other signals being equal. A seller with 99.5% positive feedback outranks an otherwise identical seller with 95% positive feedback. eBay Cassini treats seller quality as a proxy for buyer experience quality: high-quality sellers produce fewer buyer disputes, returns, and negative experiences.
Listing quality signals include price competitiveness, shipping terms, and return policy. A listing priced at or below the average sold price for comparable items scores higher on the price competitiveness signal than a listing priced above market average. Free shipping listings outrank identical listings with buyer-paid shipping, all else equal.
How Does Cassini Rank Free Shipping vs Buyer-Paid Shipping Listings?
Cassini applies a positive ranking signal to free shipping listings relative to comparable listings with buyer-paid shipping. eBay’s buyer research shows that buyers prefer free shipping listings when all other factors are comparable. Cassini incorporates this buyer preference into its ranking model. A free shipping listing and an identically priced paid-shipping listing for the same item, with all other signals equal, results in the free shipping listing ranking higher in Best Match results.
Free shipping listings display “Free shipping” in eBay search results, which attracts buyer attention and increases click-through rate. Higher click-through rates are themselves a Cassini ranking signal: listings with more click-throughs from impressions signal to Cassini that buyers find the listing relevant and appealing, which improves future ranking.
The cost of offering free shipping is absorbed into the item price when sellers apply a price increase equal to the shipping cost. A seller who charges $5 shipping on a $45 item can list at $50 with free shipping. The buyer pays the same total amount. The seller’s net revenue after the same shipping label cost is identical. The free shipping listing ranks higher in Cassini results.
The trade-off of free shipping pricing is a higher item price that may reduce price competitiveness signals. A listing at $50 free shipping competes on price against other $50 listings. A listing at $45 plus $5 shipping appears at $45 in search results (before shipping is shown) and may rank above the $50 free shipping listing on the price competitiveness signal, while ranking below it on the shipping terms signal.
How Does Listing Engagement Affect Cassini Ranking?
Cassini uses listing engagement metrics as ranking signals, including: click-through rate (percentage of search impressions that result in a click), watch rate (percentage of viewers who click Watch), and sell-through rate (percentage of listing periods that result in a sale). Listings with higher engagement relative to comparable listings receive higher Cassini scores over time. Listings that receive zero views or zero clicks over multiple listing cycles receive lower Cassini scores.
Click-through rate is the ratio of clicks to impressions. A listing that appears in 1,000 search results and receives 50 clicks has a 5% click-through rate. A listing that appears in 1,000 searches and receives 100 clicks has a 10% click-through rate. Cassini interprets higher click-through rates as evidence that the listing title, price, and thumbnail image are compelling to buyers searching for that item.
Watch rate measures buyer intent. Buyers who watch a listing without purchasing are signaling ongoing interest. A listing with a high watch rate relative to impressions indicates buyer demand for the item. Cassini interprets high watch rates as a positive buyer intent signal and may boost the listing in future search results.
Sell-through rate is the percentage of listing periods that result in a completed sale. A Good Till Cancelled listing that sells within its first 30-day period has a 100% sell-through rate for that cycle. Repeated relisting of the same item without sales produces declining sell-through rates, which Cassini interprets as declining demand or mismatch between the listing and buyer expectations.
What Changes to a Listing Improve Cassini Ranking Immediately?
5 listing changes produce immediate Cassini ranking improvement: completing all required and optional item specifics (category-specific data fields that Cassini uses for filtering), adding the primary keyword in the exact buyer search format to the listing title, setting free shipping, reducing the item price to or below the average sold price for comparable items, and offering a 30-day or 60-day return policy. Each of these changes activates positive Cassini signals without advertising spend.
Item specifics completion is the most commonly neglected ranking improvement. Categories have required item specifics (must be filled to publish) and optional item specifics (recommended but not required). Buyers who use filter tools on the left sidebar of eBay search see only listings with the filtered item specific filled. A seller whose listing lacks the Color item specific does not appear in searches filtered by Color, regardless of how well the listing title matches the buyer’s query.
Price reduction below market average is the most direct Cassini intervention available. Cassini’s price competitiveness signal rewards listings priced below comparable sold prices. A seller who reduces the price from $10 above market to $5 below market activates the price competitiveness signal and typically sees an immediate improvement in search position and sell-through rate.
Ending and relisting the item triggers a “freshness” signal in Cassini that temporarily boosts the relisted item. This manual refresh of the listing’s age signal produces a short-term visibility boost. The boost fades as the listing ages within the new 30-day cycle. Sellers who relist rather than waiting for automatic GTC renewal can time the freshness boost to coincide with peak search periods (weekday evenings, weekend mornings).