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.

How to find the keywords Cassini actually rewards

Cassini can only match your listing to searches it can read, so keyword research on eBay starts inside eBay itself rather than in a generic SEO tool. The autocomplete suggestions in the eBay search bar are drawn from real buyer queries, which makes them the cleanest signal of live demand for your category.

A second source is the completed and sold listings filter. Search your item, filter by Sold, and study the titles of the listings that actually moved: the recurring word order, the attributes buyers include, and the level of specificity all tell you what Cassini has already learned converts for that query.

Finally, check the left-hand facets eBay shows for your search. Those facets are item specifics, and any facet buyers can filter by is a field Cassini expects you to fill in. Treat every facet as a keyword slot you must claim.

• Use eBay autocomplete for head terms and the related searches strip for long-tail variants.
• Filter by Sold listings to see which phrasing already converts in your category.
• Mine the left-hand filter facets — each one maps to an item specific you should complete.
• Check international eBay sites (eBay.de, eBay.fr) when you ship abroad; buyer vocabulary differs by market.
• Avoid keywords you cannot honestly support in the listing: irrelevant terms raise impressions but destroy click-through and conversion.

Cassini vs Google: why eBay SEO is a different discipline

Sellers often apply Google SEO habits to eBay and get poor results. Google ranks documents by authority, links and topical depth; Cassini ranks products by predicted transaction value. Backlinks, meta descriptions and word count carry no direct weight inside eBay search.

Where Google rewards long-form content, Cassini rewards structured, machine-readable data: an accurate 80-character title, complete item specifics, a correct category, and a price that stands up against comparable sold items. The description matters for buyer confidence and conversion far more than for keyword matching.

The practical consequence is that improving your eBay ranking is mostly a data-hygiene exercise, repeated across every listing, rather than a content-marketing exercise.

Measuring Cassini performance in Seller Hub

Every optimization should be verified against eBay's own numbers. The Traffic report in Seller Hub shows impressions, click-through rate, and sales conversion rate per listing, which map almost one-to-one onto the three pillars Cassini scores.

Read the three metrics as a diagnostic chain. Low impressions mean a relevance problem: your title, category or item specifics are not matching the queries buyers type. Good impressions with a low click-through rate point at your first photo, title clarity or price. Good clicks with a low conversion rate point at the description, shipping cost, handling time or returns policy.

Change one variable at a time and give each change at least 14 days before judging it, because Cassini needs fresh behavioural data before it re-ranks a listing.

• Impressions down → fix relevance: title terms, category, missing item specifics.
• Click-through rate down → fix the first photo, title readability and price positioning.
• Conversion rate down → fix description, shipping cost, handling time and returns policy.
• Compare each listing against your own category average rather than against absolute benchmarks.

A practical Cassini optimization checklist

Working through the same checklist on every listing is what compounds into catalogue-wide visibility. Run it once per listing, then revisit your top sellers each quarter.

• Write an 80-character title that front-loads the buyer's search term, then brand, model, key attribute and size or colour.
• Complete every item specific eBay offers, including the optional ones, using the exact values from the dropdown.
• Confirm the listing sits in the most precise category, not a broad parent category.
• Upload at least six sharp photos: front, back, detail, scale, packaging and any flaw.
• Benchmark your price against sold listings, not active ones.
• Offer the fastest handling time you can honour reliably, and a clear returns window.
• Re-check underperforming listings monthly in the Seller Hub Traffic report and revise one variable at a time.