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How eBay’s Cassini Search Algorithm Decides What You See First
How eBay’s Cassini Search Algorithm
Decides What You See First
The listing at the top of your eBay search results didn’t get there by accident — and it wasn’t just the cheapest option. Understanding how Cassini ranks results changes how you shop, and explains why the best product isn’t always the one eBay shows you first.
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eBay Guide
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March 2026
8 min read
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maibo.uk
replaced the old Voyager
price is just one
we’ve watched it all change
Most eBay buyers assume the search results are sorted by some combination of price and relevance. That assumption is wrong, and it costs people money — both buyers who miss better products buried further down the page, and sellers who don’t understand why their listings aren’t getting seen.
eBay’s search algorithm is called Cassini. It was introduced in 2013 to replace the previous system, which ranked listings primarily by recency and price. Cassini was built around a different principle: relevance to the buyer’s likely intent, weighted by the probability that a given listing will result in a completed, satisfying transaction.
We’ve been selling on eBay since 2008. We optimised for Voyager before Cassini existed, then rebuilt our approach when Cassini launched, and have continued to refine it across the years since. What follows is what we know from the seller side — and what buyers can use to understand what they’re actually seeing when they search.
What Cassini Is Actually Trying to Do
Cassini’s core objective is not to show you the cheapest listing or the newest listing. It’s to show you the listing most likely to result in a transaction that both parties find satisfactory — a completed sale, a positive buyer experience, and no dispute or return claim.
eBay makes money on completed transactions. A listing that appears at the top of results but generates returns, disputes, or negative feedback costs eBay money in customer service, platform reputation, and buyer attrition. Cassini is designed to surface listings most likely to generate clean, completed sales. Understanding that principle explains most of what Cassini does.
Cassini doesn’t rank the cheapest listing first. It ranks the listing most likely to result in a completed sale that neither party regrets. Those are very different things.
The Seven Signals Cassini Weighs
Cassini parses your search query and matches it against listing titles, not descriptions. The 80-character title field is the primary keyword container. Sellers who build titles from actual buyer search terms rank higher for those searches — but only when the other signals also support the listing. Title relevance is necessary but not sufficient.
Cassini tracks detailed seller performance metrics — transaction defect rate, late shipment rate, cases closed without seller resolution. These are not the same as the feedback percentage visible on the profile page. A seller can maintain a 99.5% feedback score while accumulating defects that tank their Cassini ranking, because buyers resolved issues directly rather than leaving negative feedback.
eBay’s item specifics fields — brand, model, condition, MPN, colour, compatibility — are weighted heavily by Cassini because they enable precise filtering. A listing with 8 item specifics completed ranks above a comparable listing with 3 completed, all else equal. This is one of the most actionable ranking factors for sellers and the most useful filters for buyers.
Price matters — but not as most people assume. Cassini doesn’t simply favour the cheapest listing. It evaluates price relative to comparable listings in the same category, weighting click-through rate and conversion rate at the current price. A listing priced 10% above average but converting at twice the average rate signals to Cassini that buyers find the total proposition compelling — which is why an established seller can maintain premium pricing and still rank highly.
Listings with same-day or next-day dispatch receive a ranking boost because fast shipping correlates with buyer satisfaction and lower dispute rates. Free shipping also receives a boost because it improves conversion rate — a buyer comparing two equivalent listings will convert on the free shipping option more reliably.
This is the flywheel signal. Listings with strong sales history rank higher, which generates more visibility, which generates more sales, which reinforces the ranking. New listings from established sellers rank reasonably well from launch because the seller’s track record provides a proxy. New listings from new sellers start with no signal and must earn visibility through competitive pricing and item specifics completeness.
Listings with 30-day free returns rank above listings with no returns or buyer-pays returns, because Cassini treats generous policies as a proxy for seller confidence and a predictor of buyer satisfaction. Sellers who accept returns easily are selling products they stand behind. Sellers who make returns difficult are often trying to prevent buyers from discovering quality issues.
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maibo.uk
What This Means for Buyers
The first practical implication: the default “Best Match” sort on eBay is Cassini’s output. It is not neutral. It favours established sellers with strong performance histories, listings with competitive pricing relative to the category, and products with completed item specifics. A better product from a newer seller may appear lower in results simply because its sales history is shorter — not because it’s worse.
The second practical implication: using the sidebar filters dramatically improves results quality. When you filter by condition, location, item specifics, and shipping time, you’re forcing Cassini to apply your criteria precisely rather than guessing at your intent. The results after filtering are far more reliable than the default ranked list.
The third implication: price-sorted results are not “unfiltered truth.” Sorting by lowest price first surfaces listings that have deliberately undercut the category — some legitimately, many because they’re dropshipping, grey importing, or selling counterfeits. The lowest price listing is not the best deal. It’s the listing that decided price was its only competitive advantage. That’s often a warning.
✓ Use Best Match as a starting point — it surfaces sellers with strong track records
✓ Fill in all sidebar filters — item specifics filtering bypasses algorithmic guesswork
✓ Don’t sort by lowest price — it surfaces listings that compete only on cost
✓ Check the seller’s defect rate via their feedback page — it’s separate from the percentage
✓ Prioritise listings from sellers with UK dispatch and free returns — Cassini does too
What This Means for Sellers — And Why We’re Telling You
Sellers who understand Cassini build listings differently. Titles are built from actual buyer search terms. Item specifics are completed exhaustively. Pricing is set relative to category averages. Shipping is fast and free. Returns are generous. The consequence is a self-reinforcing cycle — sellers who operate this way rank higher, sell more, accumulate more history, and rank higher still.
We’re telling you this because the same knowledge that helps sellers rank higher also helps buyers identify them. A seller whose listings have complete item specifics, fast dispatch, free returns, and long account history is operating in good faith within Cassini’s framework. A seller who competes only on price and has empty item specifics fields is either new, lazy, or deliberately avoiding searchable detail. The algorithm knows the difference. Now you do too.
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maibo.uk
Cassini rewards sellers who operate transparently and penalises those who compete only on price. As a buyer, the algorithm is largely working in your favour — but only if you understand that Best Match is a prediction, not a guarantee, and that using the filters available to you makes it significantly more accurate.
Maibo on eBay since 2008. Complete item specifics. UK dispatch. Free returns. 18 years of clean sales history. We didn’t game Cassini — we just did the job properly.
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