Named after the Saturn-orbiting NASA spacecraft, Cassini is eBay's proprietary search and ranking algorithm. It was introduced around 2013 to replace a simpler "Best Match" system and has been evolving ever since. Unlike Google, which optimizes for relevance and user intent, Cassini optimizes for one thing above all else: the probability that a listing will result in a completed transaction.
That commercial-first mandate changes everything about how you should think about optimization. The most beautifully written listing in the world won't rank if buyers aren't clicking and buying. Cassini is relentlessly results-oriented — and so should your strategy be.
What follows is a breakdown of the eight primary ranking signals you can actually control, ranked roughly by their weight in the algorithm — from most to least influential.
1. Title Keywords
Your title is Cassini's primary text signal. The algorithm scans it for keywords that match buyer search queries — and gives greater weight to words that appear earlier in the title. This means your most important keyword belongs at the very start, not buried in position 5 or 6.
eBay gives you 80 characters. Use all of them, but use them intelligently. The winning formula is: [Brand] + [Model/Product Name] + [Key Attribute] + [Variant/Size/Color] + [Condition]. This structure front-loads the highest-value search terms and fills out the remaining characters with secondary descriptors that catch long-tail searches.
What Cassini doesn't reward: keyword repetition, all-caps words (buyers don't search in caps), punctuation padding, or vague descriptors like "RARE" or "NICE." These waste characters without adding search signal.
2. Item Specifics
Item Specifics are the structured data fields beneath your title — Brand, MPN, Color, Size, Material, Style, and so on. They power eBay's left-panel filters, which millions of buyers use to narrow search results. If your Item Specifics are incomplete, your listing is invisible to anyone who filters.
In 2022, eBay began requiring Item Specifics for most categories. But the requirement is easy to game — sellers enter "N/A" or "Does Not Apply" to pass the form validation. Cassini knows the difference between populated specifics and filler values, and it weights completed, accurate specifics significantly higher.
The fix: for every listing, click through every Item Specifics field. If you don't know a value, look it up (model numbers, materials, and dimensions are usually findable in 60 seconds). Only use "Does Not Apply" when it is genuinely not applicable.
3. Sell-Through Rate — The King Signal
Sell-through rate (STR) is the ratio of completed sales to total views over a given period. It is arguably Cassini's most powerful ongoing signal because it's a direct measure of listing quality as perceived by real buyers. A listing that gets views and converts into sales repeatedly tells Cassini: this listing delivers what buyers want.
The feedback loop works in both directions. High STR → better ranking → more impressions → more potential sales → even higher STR. Low STR → progressively lower ranking → fewer impressions → listing death spiral.
Managing STR requires understanding the stale listing problem. After approximately 30 days without a sale, Cassini begins deprioritizing a listing — not because the item is bad, but because its behavioral data suggests low conversion probability. The fix: end and relist. A fresh listing gets a visibility boost as Cassini re-evaluates it with fresh behavioral data.
4. Seller Performance Score
Your overall seller account health is a multiplier on every listing you create. Cassini applies an account-level modifier based on your feedback score, defect rate, late shipment rate, and "cases closed without seller resolution." A Top Rated Seller account doesn't just get a badge — it gets systematically better search placement across all listings.
The most impactful metric to maintain is your defect rate (below 2% of transactions in any 12-month period). Even a handful of unresolved INR (Item Not Received) or SNAD (Significantly Not As Described) cases can trigger a Below Standard rating that tanks your visibility sitewide.
Practical tip: ship fast, communicate proactively, and resolve disputes before they escalate to eBay. One resolved case is worth more than a dozen positive feedbacks.
5. Price Competitiveness
Cassini compares your asking price against recently sold comparable items. Listings priced significantly above the market average (more than ~20% over recent sold comps) are given lower ranking scores because Cassini predicts they won't sell — and statistically, it's correct.
This doesn't mean you can't price premium items higher. It means your listing needs to clearly justify the premium through photos, description, and completeness — because the signal Cassini actually tracks is buyer conversion, not price alone. A well-photographed, well-described listing can command higher prices while maintaining good STR.
For standard items, research "Sold Listings" on eBay before pricing. Filter by condition and set your price within the middle range of recent sold comps. This simple step eliminates one of the most common causes of invisible listings.
6. Shipping Speed & Free Shipping
eBay's "Fast 'N Free" program designates listings that offer free shipping and estimated delivery within 4 business days. Listings with this designation receive a visible badge in search results and a ranking boost. In competitive categories, the shipping badge alone can be the difference between page 1 and page 3.
Free shipping doesn't mean you absorb the cost — it means building shipping into your asking price. For lightweight, high-value items (electronics, collectibles, jewelry), this is typically straightforward. For heavy items, calculated shipping is more practical, but consider offering free shipping on your most competitive listings.
Handling time also matters. A listed handling time of 1 business day ranks better than 3 days. If you can realistically ship same-day or next-day, set it — and then actually deliver on it. Late shipments damage your seller performance score (Factor 4) which compounds negatively.
7. Photo Quality & Count
eBay allows up to 24 free photos per listing. Cassini uses photo count as a proxy for listing quality — sellers who take the time to photograph multiple angles are generally more serious, accurate sellers. Higher quality photos also directly increase click-through rate from search results, which feeds back into your STR.
The hierarchy of must-have shots: hero image on clean background → 3-4 angle shots → close-up of brand/model labels → all major defects photographed → scale reference (hand, ruler, or common object). Aim for 10-12 photos for any item over $15.
Technical minimums: 1600×1600px, no watermarks, no borders, no text overlays. eBay actively penalizes watermarked images in search. Natural light or a $30 lightbox produces better results than any smartphone filter.
8. Return Policy
Offering a 30-day or longer return policy gives Cassini a signal that you stand behind your items — which correlates with higher buyer satisfaction rates. eBay's data consistently shows that listings with returns enabled have higher conversion rates than those without, even when buyers never actually use the return option.
The fear most sellers have about returns is valid but overstated. For accurately described items with good photos, return rates are typically below 3%. The ranking benefit from enabling returns far outweighs the occasional return for the average seller. Consider it an investment in visibility.
What Cassini Penalizes
Knowing what to avoid is as important as knowing what to optimize. These are the most common Cassini penalties:
- Keyword stuffing in titles — Repeating terms or packing unrelated keywords triggers spam filters
- Watermarked photos — Actively penalized; eBay views them as barriers to buyer confidence
- Wrong category — A keyword-category mismatch is a trust signal to Cassini that something is off
- Stale listings — 30+ days with no sales = progressive deranking; relist to reset
- "N/A" Item Specifics on relevant fields — Treated nearly as poorly as blank specifics
- HTML-heavy descriptions — eBay is phasing these out; modern structured descriptions perform better
- Late shipments — Each late shipment raises your defect rate and lowers your seller performance multiplier
The AI Advantage: Optimizing All 8 at Once
The challenge with Cassini optimization is that it's not one thing — it's eight things, all of which need to be right simultaneously, across every listing. For a seller with 50+ items, manually auditing every factor on every listing is a full-time job.
This is where AI listing tools fundamentally change the economics. FlipToolz automatically generates Cassini-optimized titles (correctly front-loaded, no stuffing), populates all relevant Item Specifics from photo analysis, suggests pricing based on sold comps, and formats descriptions in the modern structured style eBay's algorithm rewards.
In early beta testing, listings created with FlipToolz averaged 31% more impressions in their first two weeks compared to manually created listings from the same sellers. The difference wasn't one factor — it was consistent execution across all eight.
Let AI Handle the Cassini Optimization
FlipToolz takes care of every ranking signal automatically — title, specifics, pricing, format. Join the waitlist for early access and listing credits.
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