What Is eBay's Cassini Algorithm (And Why It Still Matters in 2026)

If you've ever listed something on eBay and wondered why one listing rockets to page one while another identical item collects dust on page twelve, you've already felt the invisible hand of Cassini at work.

Cassini is eBay's search engine — the system that decides which listings surface when a buyer types "vintage Levi's 501 jeans" or "Sony WH-1000XM5 headphones." eBay launched Cassini back in 2013 to shift focus away from pure keyword stuffing and toward something more nuanced: buyer intent and relevance. More than a decade later, the core philosophy hasn't changed, but the algorithm has gotten considerably smarter.

In 2026, Cassini weighs dozens of ranking signals simultaneously. Understanding which ones matter most is the difference between selling consistently and watching your listings age out without a single offer.

This guide breaks down exactly how to optimize your listings for Cassini — from title construction to seller metrics — using tactics that actually work in today's market.

1. How Cassini Actually Ranks Listings

Before you can optimize anything, you need to understand what Cassini is trying to do. Its job isn't to reward clever sellers — it's to show buyers the most relevant, trustworthy item for their search query. Every ranking factor flows from that goal.

The Core Ranking Signals

Relevance is the foundation. Cassini analyzes whether your listing matches what a buyer is actually searching for. This includes:

Keywords in your title
Item specifics you've filled out
Category placement
Product identifiers (UPC, EAN, ISBN, ePID)

Seller quality plays a surprisingly large role. According to eBay's internal seller standards documentation, accounts with Top Rated Seller status receive a significant boost in search placement. This isn't just about feedback percentage — it includes transaction defect rates, late shipment rates, and cases closed without seller resolution.

Listing completeness signals to Cassini that your item is worth showing. Listings with full item specifics, multiple high-quality photos, and thorough descriptions consistently outrank sparse ones, even when the price is similar.

Price competitiveness matters too. Cassini doesn't just reward the cheapest listings, but it does factor in whether your price — including shipping — is in line with comparable sold items.

Engagement signals like click-through rate, watch count, and offer activity all feed back into Cassini's ranking decisions. A listing that buyers interact with gets rewarded with more visibility.

2. Keyword Research and Title Optimization

Your title is the single most important piece of real estate in your entire listing. Cassini reads titles heavily when matching listings to search queries, and you only get 80 characters to work with. Every word needs to earn its spot.

Think Like a Buyer, Not a Seller

The biggest mistake resellers make is writing titles for how they think about an item rather than how a buyer searches for it. You might call something a "lovely Art Deco brooch" — a buyer types "gold tone flower pin 1940s vintage."

Buyer-intent keywords are specific, functional, and often include:

Brand name (Nike, Pyrex, Levi's, Sony)
Model number or specific product line (501, Pattern #475, Air Max 90)
Size or measurements (XL, 10.5 Men's, 8x10)
Condition descriptors (vintage, NWT, NWOT)
Color or material when relevant
Era or decade for vintage items

Building a High-Performing Title

Here's a practical framework. Start with the most critical search term, then layer in qualifying details:

Weak title: Vintage Levi's Jeans Nice Condition Blue Denim

Strong title: Levi's 501 Jeans Vintage 90s Men's W34 L32 Dark Wash Straight Leg

The second title hits multiple buyer searches: people searching by fit, by decade, by waist size, by wash. It also avoids filler words like "nice" and "great" that Cassini ignores and buyers don't search for.

Tools for Keyword Research

eBay's own search bar is your first stop. Type your item and watch the autocomplete suggestions — those are real buyer searches.
eBay's Terapeak (included free with eBay Store subscriptions) shows you what search terms are driving sales in any category.
Completed/Sold listings tell you what titles are working for items that actually sold. If a sold listing for your item uses specific language, that's a signal worth paying attention to.

For more eBay SEO best practices around titles specifically, this guide to eBay title examples for vintage thrift clothing has strong real-world examples worth studying.

What NOT to Include in Titles

Exclamation points or all-caps words
Subjective descriptors ("beautiful," "amazing," "rare" unless it genuinely is)
Your store name or policies
Repeated keywords (Cassini ignores them and buyers find it annoying)

3. Images: The Silent Ranking Factor

Here's something a lot of resellers overlook: Cassini measures engagement, and nothing drives engagement like images. A listing with sharp, well-lit photos gets more clicks, more watches, and more time-on-page — all signals that tell Cassini this listing deserves better placement.

The 6-8 Photo Rule

eBay allows up to 24 photos per listing for free. Mobile-optimized listings with 6-8 high-quality images consistently show higher click-through rates than listings with 1-3 photos, according to eBay seller data. For casual sellers that might feel like overkill, but for resellers competing in crowded categories, it's table stakes.

The essential shots for most items:

Hero shot — clean, centered, white or neutral background
Back or secondary angle
Any branding or labels (especially important for authentication)
Close-up of condition issues (even small ones — hiding flaws kills your seller ratings)
Measurements or size tag
Any included accessories, original packaging, or documentation

For clothing, add shots of the tag, waistband/collar, and any wear or fading. For electronics, show all ports, the screen, and any original accessories.

Mobile Optimization Is Non-Negotiable

More than 60% of eBay transactions now involve mobile at some point in the buying journey. Your photos need to read well on a 6-inch screen. That means:

High resolution (minimum 500px on the longest side, ideally 1600px+)
Bright, even lighting — natural light near a window or a simple lightbox works well
No cluttered backgrounds that distract from the item
Square crop for the hero image performs better in search results on mobile

If you're photographing thrift flips, this deep-dive on photographing thrift clothes for eBay is worth bookmarking — the lighting tips alone are genuinely useful.

4. Item Specifics and Structured Data: The Underrated Edge

Item specifics might be the most consistently underutilized optimization lever on eBay. Sellers fill in the required fields, skip the optional ones, and wonder why their listings don't rank.

Why Item Specifics Matter So Much

Cassini uses item specifics as structured data — essentially metadata that helps the algorithm categorize and match your listing to buyer searches with precision. When a buyer uses eBay's filter sidebar to narrow down results by size, color, brand, condition, or era, your listing only appears if you've filled in those fields.

Think about what that means in competitive categories. If you're selling a vintage Pendleton shirt and you haven't filled in "Pattern: Plaid," "Material: Wool," and "Decade: 1970s," your listing is invisible to every buyer who filters by those attributes.

Product Identifiers (UPCs, ISBNs, ePIDs)

For new or newer items with barcodes, including the GTIN/UPC or ePID (eBay Product Identifier) gives your listing a significant boost. These identifiers connect your listing to eBay's product catalog, which means:

Your listing can appear in eBay's product-level search results
You may qualify for Google Shopping integration
Cassini treats catalog-matched listings as higher quality signals

For vintage and handmade items without UPCs, select "Does Not Apply" rather than leaving the field blank — this tells Cassini you've addressed the field intentionally.

Filling Out Every Relevant Field

Beyond identifiers, make it a habit to fill in every item-specific field that's relevant, including optional ones. A Nike Air Max 90 listing should include:

Brand: Nike
Model: Air Max 90
Size (US): 10.5
Color: White/Black
Department: Men
Shoe Width: Medium
Style: Sneaker
Upper Material: Leather

That might feel excessive, but each field you fill in is another search filter your item can match.

5. Description Best Practices

While Cassini doesn't weight descriptions as heavily as titles for keyword matching, descriptions still matter — both for buyer confidence and for long-tail search scenarios.

Write for Humans First

Your description should answer the questions a buyer would ask before purchasing:

What exactly is it? (Be specific — dimensions, weight, model number)
What condition is it in? (Be honest about any flaws)
What's included? (Original box? Accessories? Documentation?)
How will it be shipped? (Handling time, carrier, packaging method)

Keep formatting clean. Long walls of text hurt mobile readability. Use short paragraphs and bullet points for condition notes.

Avoid Description Keyword Stuffing

Repeating keywords in the description 10 times won't help and may actually hurt. Cassini is sophisticated enough to recognize natural language. Write like you're describing the item to a friend.

6. Seller Ratings, Shipping, and the Trust Signals That Boost Rankings

Here's where a lot of newer resellers get frustrated — you can have a perfectly optimized listing and still lose ground to competitors because of seller account health metrics. Cassini bakes trust signals into the algorithm at an account level, not just a listing level.

Seller Standards and Top Rated Status

eBay's Top Rated Seller status comes with documented search benefits. To qualify (and maintain the boost), you need:

98% or higher positive feedback
Transaction defect rate below 0.5%
Late shipment rate below 3%
Cases closed without seller resolution below 0.3%

These aren't just bureaucratic thresholds — each one represents a real buyer experience signal. Maintaining them consistently is part of the long game of eBay SEO.

For a practical roadmap to keeping your feedback where it needs to be, this seller reputation guide covers the specifics in detail.

Shipping: Free or Competitive Rates

Cassini gives preferential ranking treatment to listings that offer free shipping or low-cost flat-rate shipping. The logic is straightforward: buyers hate shipping surprises, and eBay knows it.

If your margins allow it, roll shipping into your price and offer free shipping. A $25 item with free shipping often ranks higher and converts better than a $20 item with $5 shipping — even though the buyer pays the same amount.

For items with predictable shipping weights (most clothing, books, small electronics), eBay's Calculated Shipping ensures you're not losing money on orders while still offering competitive rates. eBay's shipping setup guide for thrift store flips walks through the setup process if you haven't configured it properly yet.

Handling Time

Listings with 1-day or same-day handling receive a ranking boost. This doesn't mean you have to ship instantly, but committing to fast handling — and actually meeting that commitment — improves both your seller metrics and your search placement.

Response Rate

eBay tracks how quickly and consistently you respond to buyer messages. A high response rate signals a reliable seller, which factors into your overall account health score and, by extension, your Cassini ranking.

7. Pricing and Cassini: What the Algorithm Actually Sees

Cassini doesn't simply reward the lowest price — it evaluates price in context. A $150 listing for a Pyrex mixing bowl set might rank well if comparable sold items support that price. An outlier pricing strategy (going dramatically above or below market) can actually hurt visibility.

This is where solid pricing research matters. Tools like Terapeak, completed listings, and apps that surface real-time sold data help you price competitively without leaving money on the table.

If you're still working out your pricing approach, this eBay pricing strategy guide for resellers covers the full methodology including how to use comp sales effectively.

Putting It All Together

Optimizing for Cassini isn't a one-and-done task. It's a set of habits that compound over time:

Research keywords before you list — use autocomplete and sold listings, not guesswork
Build titles with buyer-intent terms — brand, model, size, condition, material
Photograph every item properly — 6-8 clean images optimized for mobile
Fill in every relevant item specific — especially optional fields and product identifiers
Maintain your seller metrics — feedback, defect rate, shipping speed
Price competitively with shipping factored in — free shipping where margins allow
Write honest, clear descriptions — they build trust and close sales

The resellers who dominate eBay search in 2026 aren't necessarily the ones with the biggest inventory or the most ad spend. They're the ones who've internalized eBay SEO best practices and apply them consistently, listing after listing.

If you're sourcing regularly from thrift stores or estate sales and listing dozens of items a week, tools that help you research pricing and identify what's worth listing quickly — like Underpriced AI's scan-to-price feature — can cut the research time significantly and help you focus on the optimization work that actually moves the needle.

The algorithm is beatable. It just takes knowing the rules before you play.

How to Optimize eBay Listings for Cassini Algorithm in 2026: Complete Guide