Understanding eBay's Cassini Algorithm and Why It Controls Your Sales

If you've ever listed something on eBay and watched it sit with zero views for weeks, the Cassini search algorithm is usually the culprit — or the solution, depending on how well you've optimized.

eBay's Cassini algorithm (named after the Saturn-orbiting spacecraft, fittingly ambitious) replaced the older Voyager system back in 2013, but it's grown significantly more sophisticated in the years since. In 2026, it evaluates listings across dozens of ranking signals simultaneously, and understanding those signals is the difference between a listing that sells in three days and one that collects dust for months.

The Core Ranking Factors Cassini Cares About

Relevance is the foundation. Cassini matches buyer search queries against your listing's title, item specifics, category, and description. If the right keywords aren't present, the algorithm simply can't surface your listing — no matter how good the item is.

Seller performance metrics carry enormous weight. Your defect rate, late shipment rate, and cases closed without seller resolution all factor into where your listings appear. According to eBay's seller performance standards, accounts with a Top Rated Seller status can see up to a 10% boost in search placement compared to below-standard sellers. This is one area many resellers overlook when troubleshooting visibility problems.

Sales history and conversion rate tell Cassini how well your listings perform once buyers find them. A listing with a strong click-through rate and purchase rate gets rewarded with higher placement. This creates a compounding effect — optimized listings sell faster, which improves seller metrics, which improves future listing visibility.

Listing completeness — specifically filled-out item specifics — has become a harder requirement since eBay's 2023 policy updates, which introduced penalties for incomplete data in high-demand categories.

Pricing competitiveness relative to sold comps also plays a role. eBay wants buyers to find fair prices, so wildly overpriced listings get nudged down in results even when the keywords are perfect.

Keyword Optimization: Writing eBay Titles That Actually Rank

This is where most sellers either win or lose the visibility game before a buyer ever clicks. eBay gives you 80 characters for your title. Every character should be working for you.

Why Mid-Tail Keywords Outperform Everything Else

Broad single keywords like "jacket" or "camera" have enormous search volume but insane competition — you're going up against thousands of listings. Hyper-specific long-tail phrases like "1987 Levi's 550 relaxed fit orange tab denim jeans 34x32 made in USA" are accurate but often too specific to capture casual browsing traffic.

The sweet spot for eBay SEO optimization is mid-tail keywords — 3 to 5 words that combine item type, key attributes, and buyer intent. Examples:

"vintage Levi's denim jacket 90s" (not just "denim jacket")
"Sony a6000 mirrorless camera body" (not just "Sony camera")
"cast iron skillet Lodge 12 inch pre-seasoned" (not just "cast iron skillet")

These phrases carry meaningful search volume while facing less competition than single-word terms. They also align with how real buyers actually search when they're in purchase mode, not just browsing.

Title Structure Best Practices for 2026

Lead with the most important keyword. Cassini gives more weight to words earlier in the title. If you're selling a vintage Band-Aid tin, "Vintage Band-Aid Tin Collectible Metal Box Red Cross 1950s" outperforms "1950s Red Cross Metal Box Collectible Vintage Band-Aid Tin."

Include attributes buyers filter by: brand, model, size, color, era, condition. These aren't just helpful — they're what Cassini uses to match filtered searches.

Avoid keyword stuffing and filler words. Words like "look," "nice," "wow," "L@@K," and "see description" waste character space and don't help ranking. So do articles like "a," "an," and "the" unless absolutely necessary.

Use eBay's own search suggest tool for free keyword research. Start typing your item in eBay's search bar and let the autocomplete show you what buyers are actually searching. This is one of the most underused eBay keyword research tools available, and it's free.

For a deeper breakdown of how to structure titles specifically for clothing categories — one of the trickiest niches — check out Best eBay Title Examples for Vintage Thrift Clothing | Boost Sales in 2026.

Item Specifics: The Hidden Ranking Factor Most Sellers Ignore

eBay has been aggressive about pushing sellers to complete item specifics, and in 2026, it's no longer optional in practical terms. Incomplete item specifics in categories like clothing, electronics, collectibles, and automotive parts can trigger what eBay internally calls "de-ranking" — your listing gets buried below competitors whose data is complete.

What Counts as "Required" vs. "Recommended"

eBay labels some fields as required and others as recommended, but the algorithm treats both seriously. Required fields left blank can prevent a listing from appearing in filtered searches entirely. If a buyer searches for "men's jackets" and filters by size "Large," your listing won't appear if you didn't fill in the size field — even if the word "Large" appears in your title.

Recommended fields are almost as important. A 2024 study by eBay's seller analytics team found that listings with 100% of item specifics completed (including recommended fields) had significantly higher impressions and sell-through rates than listings with only required fields filled in.

Practical Item Specifics Strategy

Use eBay's pre-populated suggestions when they appear. These are pulled from real catalog data and are already optimized.
Add custom item specifics for attributes that eBay's form doesn't automatically include. For vintage items, this might be "Decade: 1970s" or "Country of Origin: USA."
Be accurate. Filling in specifics with inaccurate data to game filters leads to returns, negative feedback, and eventually account penalties.
Condition notes matter. Use the condition description field to explain any flaws. This actually increases buyer confidence rather than hurting conversions — buyers know what they're getting.

For resellers working in fashion specifically, accurate sizing and condition data is critical. Selling Secondhand Fashion Online: Sizing, Descriptions & Profit Tips covers the nuances in that category in detail.

Photo and Description Optimization: Converting Clicks Into Sales

Getting visibility is only half the battle. Once a buyer clicks your listing, your photos and description have to close the sale. Cassini also tracks listing conversion rate, so weak photos don't just hurt sales — they hurt future search placement.

Photo Standards That Reduce Returns and Increase Sales

eBay's own data consistently shows that listings with 6 or more high-quality photos convert better and generate fewer returns. In 2026, eBay allows up to 24 photos at no additional cost. Use them.

Practical photo checklist:

Main photo on white or neutral background — this is what shows in search results and dramatically affects click-through rate
All four sides for three-dimensional items (electronics, collectibles, ceramics)
Flat lay and worn/modeled shots for clothing — modeled photos increase clothing conversions by an estimated 20-30% based on reseller community data
Close-up shots of brand tags, labels, and hallmarks for authentication and search discovery
Flaws clearly documented — a close-up of a small stain or chip builds trust and prevents "item not as described" cases

Natural lighting beats flash photography in almost every scenario. A $0 setup — item on a white foam board near a window — outperforms expensive ring lights used in a dark room.

If you're selling thrift clothing specifically, Best Way to Photograph Thrift Clothes for eBay | Pro Tips for 2026 Sellers goes deep on setup and technique.

Writing Descriptions That Serve Both Buyers and SEO

Your description is less critical for Cassini ranking than it was five years ago — most ranking signals now come from title, specifics, and seller metrics. But descriptions still matter for buyer conversion and for appearing in Google Shopping results.

Effective description structure:

Lead with key details — what it is, brand, size, condition
Expand on features and appeal — why someone would want this, what makes it unique
List measurements for clothing and furniture (never just "see photos" — specify in the listing)
Address likely buyer questions preemptively — does it have original box? Is it tested and working?
Shipping and return policy reminders — reduces friction and improves buyer confidence

Avoid copying manufacturer descriptions verbatim. eBay's algorithm can identify duplicate content, and it doesn't add any ranking value.

Pricing Strategy: Where Market Research Meets Algorithm Optimization

Pricing is where improve eBay listing visibility and actual profitability intersect. Cassini rewards competitive pricing, but that doesn't mean pricing to the bottom — it means pricing intelligently based on real market data.

How to Research Comps Before You Price

The "sold listings" filter in eBay's advanced search is your baseline. Filter by condition, time period (last 90 days for most items, last 30 days for fast-moving categories), and listing format. This shows you what buyers have actually paid — not just what sellers are hoping to get.

For items with significant value variability — vintage electronics, antiques, designer pieces — tools like Terapeak (included free for eBay Store subscribers) can show 12 months of historical pricing data with detailed breakdowns. Best Product Research Tools for eBay Resellers in 2026: Terapeak & Beyond covers the full toolkit worth using in 2026.

The Pricing Signals Cassini Responds To

Cassini monitors your price relative to similar sold listings. A listing priced 40% above recent comps will rank lower than a competitively priced listing, even if every other optimization is perfect. The algorithm is designed to connect buyers with fair deals.

That said, lowest price doesn't win automatically. Cassini weighs seller feedback score, listing quality, and shipping terms alongside price. A Top Rated Seller with a competitive (not lowest) price often outranks a new seller pricing 15% lower.

Best Offer is an underused ranking tool. Listings with Best Offer enabled get slightly better visibility in some categories because eBay considers them more buyer-friendly. It also opens the door to price negotiation, which can move inventory that would otherwise sit.

For a complete framework on pricing thrift and estate sale finds profitably — including the math behind ROI targets — read eBay Pricing Strategy for Resellers: How to Price Items for Maximum Profit.

Additional Factors That Move the Needle in 2026

Seller Metrics Are Non-Negotiable

This deserves emphasis: no amount of keyword optimization compensates for poor seller metrics. If your late shipment rate is above 3% or your defect rate is elevated, Cassini actively suppresses your listings. Maintaining Top Rated Seller status isn't just about the badge — it's an algorithmic advantage that affects every single listing you have.

Listing Format: Auction vs. Fixed Price

Fixed-price Good 'Til Cancelled (GTC) listings generally outperform auctions for search visibility in 2026. Auctions cycle off quickly and lose the ranking history they've accumulated. Fixed-price GTC listings build sale history and conversion data over time, which compounds into better placement.

Reserve auctions in particular get penalized — Cassini treats high reserves as a sign of low buyer-friendliness.

The Role of Promoted Listings

eBay's Promoted Listings Standard (pay-per-sale ad model) can supplement organic visibility, but it's not a substitute for optimization. An unoptimized listing with a high promotion rate will still underperform a well-optimized organic listing in many cases. Think of promotions as amplifying a good listing, not rescuing a bad one.

If you're weighing whether to spend on promotions or invest more time in organic optimization, eBay Promoted Listings Changes 2026: Should You Switch to Organic SEO? breaks down the current cost-benefit calculation.

Putting It All Together

Optimizing eBay listings for better visibility in 2026 isn't about any single tactic — it's a system where every component reinforces the others. A perfectly keyworded title gets undermined by incomplete item specifics. Great item specifics don't help if photos are driving buyers away. Competitive pricing matters, but not if seller metrics are dragging everything down.

The resellers who consistently dominate search results aren't necessarily the ones with the most inventory or the biggest ad budgets. They're the ones who treat each listing as an optimization project: researching keywords before writing the title, photographing items thoroughly before listing, filling in every item specific field, and pricing based on actual sold data rather than optimism.

If you're sourcing from thrift stores or estate sales and want to know what's actually worth optimizing for — which items have the comp data to support a solid listing strategy — tools like Underpriced AI can give you that pricing intelligence at the point of sourcing, before you even get home. But regardless of what tools you use, the listing fundamentals covered here are what ultimately determine whether eBay's algorithm works for you or against you.

The algorithm isn't your enemy. It's just a system that rewards sellers who put in the work.

How to Optimize eBay Listings for Better Visibility in 2026: Complete Guide