eBay Cassini: How eBay's Search Engine Ranks Listings in 2026

What is Cassini and how does it work?

Cassini is the search engine eBay has used since 2011 to power its default "Best Match" sort order. Unlike a simple keyword match, Cassini analyzes hundreds of signals for every search query and every active listing to predict which items a buyer is most likely to click on and purchase.

The goal of Cassini is not to reward the seller who lists the most keywords or the lowest price alone — it is to maximize the probability of a completed, satisfying transaction. That means it constantly re-ranks listings based on real buyer behavior: clicks, add-to-carts, purchases, returns, and even how quickly an item sells after being listed.

Because Cassini is a learning system, its exact weighting shifts over time as eBay tunes it. But the core pillars — relevance, item specifics, listing quality, and seller performance — have remained stable for years and are the safest areas to focus your optimization effort on.

The main ranking factors Cassini evaluates

Cassini blends dozens of signals, but they can be grouped into a handful of practical categories that every seller should track.

• Relevance: how well your title, item specifics, and category match the buyer's search terms.
• Listing quality and conversion rate: click-through rate, sales conversion, and how complete your listing is (photos, description, specifics).
• Seller performance: Top Rated Seller status, defect rate, late shipment rate, and case/return history.
• Price and shipping: price competitiveness relative to similar listings, and whether you offer free or fast shipping.
• Returns policy: listings with clear, buyer-friendly return policies tend to convert better and are favored.
• Sell-through and freshness: items with strong sell-through rates and up-to-date stock/availability signals.

Optimizing your title for Cassini

The title is the single most important relevance signal Cassini reads. eBay titles have a strict limit of 80 characters, so every word must earn its place. Front-load the terms buyers actually type: brand, model, key attribute (size, color, capacity), and product type, in the order a shopper would search.

Avoid keyword stuffing — repeating the same word, adding unrelated terms, or stacking synonyms that don't reflect the item. Cassini's relevance model is trained to detect stuffing and irrelevant keywords, and it demotes listings that try to game the system rather than describe the product accurately.

A well-built title reads naturally, matches how real buyers phrase their searches, and covers the two or three attributes most likely to be filtered on. Testing different keyword orders and monitoring impressions is the most reliable way to refine a title over time.

Why item specifics matter more than most sellers think

Item specifics (brand, size, color, material, model number, and category-specific fields) are not just cosmetic details — they feed the structured-data filters buyers use on the left side of search results. When a buyer filters by "Size: 10" or "Color: Black", eBay can only show your listing if that specific is filled in correctly.

Missing or inaccurate specifics don't just hide you from filtered searches; they also lower Cassini's confidence in your listing's relevance, since specifics are one of the clearest, most machine-readable relevance signals available. Filling in every recommended field, even the optional ones, gives Cassini more data to match your item to the right searches.

Listing quality and conversion signals

Cassini watches how buyers actually behave once they land on your listing. A high click-through rate followed by a low sales conversion tells Cassini something about your listing isn't matching expectations — often price, photos, or description quality.

Clear, well-lit photos from multiple angles, a complete and honest description, and a price that's competitive with similar sold listings all contribute to conversion. Listings with a Buy It Now option, fast handling time, and free or discounted shipping also tend to convert better, and Cassini rewards that with improved placement.

It's worth periodically reviewing your own listings the way a buyer would: does the first photo clearly show the item, is the title matching the photo, and is the price justified by the condition and specifics you've listed?

Seller performance and account health

Beyond the listing itself, Cassini factors in your account-level performance. Metrics like defect rate, late shipment rate, and cases closed without seller resolution all feed into your eBay seller standing, and a poor standing can suppress visibility across your entire inventory, not just one listing.

Achieving and maintaining Top Rated Seller status — which requires low defect rates, fast shipping, and a solid transaction history — gives an additional visibility boost in search and can qualify listings for the Top Rated Plus badge, which buyers trust and click more often.

Common mistakes that hurt your Cassini ranking

Most sellers lose ranking not because of one big error but because of small, repeated mistakes across their catalog.

• Stuffing titles with unrelated brand names or excessive keywords instead of the terms buyers actually search.
• Leaving item specifics blank or picking the closest option instead of the accurate one.
• Letting handling time slip, which increases late shipment rate and hurts seller standing.
• Ignoring returns and cases, which raises your defect rate and signals poor buyer experience.
• Copy-pasting the same title and description across very different variations without adjusting specifics.
• Never revisiting listings — Cassini rewards freshness and updated, accurate information over static, outdated listings.