eBay Cassini search algorithm: what eBay says ranks a listing, and the myths to ignore

What is the eBay Cassini search algorithm?

The eBay Cassini search algorithm is the system that decides which listings a buyer sees, and in what order, when they search eBay with the default "Best Match" sort. Cassini is the name eBay gave its search engine when it was rebuilt, and sellers still use the name today. On its own help pages eBay usually talks about Best Match rather than Cassini, but they refer to the same thing: the ranking that applies unless a buyer chooses another sort such as lowest price or newly listed.

Nobody outside eBay knows the full formula, and eBay changes it over time. What eBay does publish is the list of factors Best Match considers. That list is the most reliable guide you have, and it is far more useful than the rumours that circulate in seller forums.

Which ranking factors does eBay say Best Match uses?

eBay names these factors in its guide to optimising listings for Best Match:

eBay does not say how much weight each factor carries, and it is reasonable to assume the balance differs between searches. eBay also advises filling in item specifics such as make, model, size, colour and style, which touches both the "matches the search" and "complete listing" factors.

How does Cassini decide relevance?

Relevance is the first filter. If a listing does not match what the buyer typed, no amount of popularity will put it in front of them. Relevance comes mainly from:

• The title. The words buyers search for, in plain language, such as brand, product type and model. An eBay title can be at most 80 characters.
• The category. A listing in the wrong category can be matched poorly or filtered out when buyers browse.
• Item specifics. Structured details let eBay match filtered searches such as "Size: 10" or "Brand: Bosch".
• Product identifiers. Codes such as EAN, UPC or MPN help eBay tie the listing to the right product.

A practical point: relevance can work against you as well. Stuffing a title with loosely related words can show the listing to buyers who did not want it. They scroll past, and a listing that is shown often but rarely chosen is not sending the signals you want.

Why the same listing ranks differently for different searches

Ranking is worked out per search, not per listing. Your cordless drill might sit near the top for "18v cordless drill brushless" and far down for "drill", because the first search matches your title closely and the second matches thousands of listings equally well. This is why checking your position for one broad word tells you very little. Test the longer phrases buyers really type, and judge a listing by the searches that bring it sales.

It also explains why two sellers of the same product can both do well. Each title matches a slightly different set of searches. Covering the most common way buyers describe the item, plus one or two accurate alternatives, widens the set of searches you are relevant for without turning the title into a list.

Why do popularity and price matter so much?

Among relevant listings, eBay wants to show the ones buyers are most likely to buy. Popularity and price are how it judges that. A listing that buyers click and buy is a safer result to show than one they ignore.

This is why the listings with a sales history are hard to dislodge, and why new listings can take time to settle. It is also why a sharp price matters. Price here is what the buyer pays, so a low item price with high postage does not look cheap to a buyer comparing totals.

Example (hypothetical): suppose two sellers list the same desk lamp. Seller A charges £19.99 with free postage. Seller B charges £16.99 plus £3.99 postage, a total of £20.98. Seller A's total is lower and the offer is simpler to read, which can make buyers more likely to choose it. The numbers are illustrations, not eBay data.

Do returns, handling time and seller performance affect ranking?

Yes, eBay lists them as factors. Listing terms such as the return policy and handling time are named directly, and so is the seller's track record. You cannot see your own "search score", but you can see the inputs:

• Handling time. Set one you can always meet. A short handling time that you miss will hurt your record more than a slightly longer one that you hit.
• Returns. A clear returns policy reassures buyers. On eBay UK, business sellers must have a returns policy stating how long buyers have to return items for a full refund.
• Seller performance. eBay UK evaluates sellers on the 20th of each month on defects, cases closed without seller resolution and late deliveries. Below Standard can mean selling limits and higher final value fees, as eBay's seller performance policy explains.

For dropshippers, the track record factor is where supplier problems turn into search problems. Every late parcel, cancellation and case counts against you, whoever caused it. eBay allows dropshipping from a wholesale supplier, but buying from another retailer or marketplace that ships directly to your buyer is not allowed, and you stay responsible for delivery and buyer satisfaction either way.

Which Cassini myths can you ignore?

Seller forums are full of tricks that promise to beat the algorithm. Most rest on guesswork. Here are common ones and a more useful way to think about each.

• "Ending and relisting resets your ranking upwards." Ending a listing also ends its sales history, which is part of popularity. Relisting can make sense for a listing that never sold, but it is not a reliable boost.
• "Keywords in the description rank you." The description matters for listing quality and for buyers, but the title, category and item specifics carry the search match. Writing a block of keywords in the description can break eBay's rules on keyword spamming.
• "Revising a listing hurts it." Fixing a wrong title or missing specifics is usually better than leaving an error live. Make useful changes, not constant ones, so you can tell what worked.
• "There is a secret hour to list." eBay does not publish any best listing time for fixed price items, which stay live until they sell or you end them. Focus on what eBay does name.
• "Promoting is the only way to get seen." Promoted Listings place ads in search results, which is separate from organic Best Match. Promotion can add visibility, but a weak listing stays weak when promoted.

How can you improve your Best Match position this week?

1. Fix relevance. Rewrite titles that open with filler. Lead with brand, product type and model.
2. Complete item specifics. Fill every required and recommended field with accurate values. Our guide to eBay item specifics walks through it.
3. Check photos. eBay's picture policy requires photos of at least 500 pixels on the longest side and bans borders, added text and watermarks.
4. Review the total price. Compare your item price plus postage with similar sold items.
5. Set handling times you meet. Then meet them every time.
6. Keep stock accurate. An item that sells and then has to be cancelled damages your record. A tool such as Dropizon can set quantity to zero when a source shows out of stock; see how it works.

What to do next

Pick your ten most viewed listings that have no recent sales. For each one, check the title, category and item specifics for relevance, then the photos and total price for quality and value, then your handling time and returns policy. Make the changes, note the date and review your Seller Hub traffic report after a few weeks. Treat the Cassini search algorithm as a set of buyer-focused signals, not a puzzle to trick, and work through eBay's own list in order.