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Why Do Zalando and ASOS Marketplace Keep Rejecting or Mangling Our Clothing Sizes?

Fashion brands selling on Zalando or ASOS Marketplace fight size and attribute rejections. We map your sizes and attributes once and keep listings in sync.

Updated 3 min readBy SpiderHunts Technologies

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Quick answer — TL;DR

Fashion marketplaces want sizes, colours and attributes in their own lists, and your store uses yours, so listings get rejected or sizes get mapped wrongly by hand. We build a mapping layer between your product data and each marketplace's size and attribute lists, validate every listing before it is sent and keep stock and prices in step.

A spreadsheet upload and a page of errors

You have been accepted onto a fashion marketplace. Great news, until the first upload. The marketplace wants sizes from its own list: your 'UK 10' has to become their size code, your 'S/M' does not exist at all, and your jeans sized '28' need a length too. Colours have to be picked from their colour family list. Every product needs attributes you have never recorded: neckline, sleeve length, pattern, occasion.

Someone on your team spends days filling in a template. The upload comes back with errors. They fix them, upload again, get more errors. When stock changes, the marketplace does not always know, and you sell a dress there that sold out on your site that morning.

Why marketplaces are harder for fashion

  • Every marketplace has its own size lists, and they differ by category and by country.
  • One-size, dual sizes like S/M, and numeric denim sizes rarely map cleanly.
  • Marketplaces require attributes your store does not hold.
  • Colour names must match their colour families, not your creative names.
  • Stock and prices need to stay in step with your store, several times a day.

Generic marketplace connectors handle stock and orders well. The fiddly part in fashion is the size and attribute mapping, and that is usually left to a spreadsheet.

What bad mapping costs

ProblemWhat you see
Rejected listingsStyles missing from the marketplace for weeks
Wrong size mappingReturns because the customer got a different size
Missing attributesProducts not found in the marketplace's filters
Stock out of stepCancellations that hurt your seller rating
Manual templatesDays of work every season

How we map sizes and attributes once

  1. We collect your size ranges per product type and map each size to the marketplace's size list for that category and market. Awkward cases like S/M and denim waist-and-leg sizes get explicit rules, agreed with you.
  2. Your colour names are mapped to the marketplace's colour families, so 'Sage' becomes their green without changing your own name.
  3. Required attributes are held as fields on your products. Where you have none, a language model drafts them from your product data and photos, and your team checks them before they are used.
  4. Before any listing is sent, it is checked against the marketplace's rules, and anything missing is listed for your team with a clear reason.
  5. Listings are sent through the marketplace's own API or approved connector, and stock and prices are updated on a schedule, with a buffer you choose so the last unit is not sold twice.
  6. Orders come back into your store or order system, so your warehouse picks them in the normal way.

Where a connector you already use handles the transport, we build only the mapping and validation on top of it.

A new season afterwards

New styles are set up in your store as normal. The mapping layer knows that a 'dresses, UK 6 to 18' range maps to a set of marketplace sizes, and that your 'Sage' is green. The check lists three products missing a sleeve length. Someone fills them in, and the listings go through first time. When a size sells out on your site, it comes off the marketplace within the next update.

More than one marketplace

Selling on two or three marketplaces multiplies the work, because each has its own lists. The mapping layer holds a set of mappings per marketplace and per country, all from the same product data. Adding a new market means adding one set of mappings, not starting a new spreadsheet. Your size chart data, if you hold it per range, can feed each marketplace's size information too.

Marketplaces change their lists and rules from time to time. When a listing starts failing validation after a change on their side, the check shows it straight away with the field that changed, so it is fixed in one place rather than product by product.

Signs your marketplace listings need this

  • Uploads to a marketplace come back with size or attribute errors.
  • Size mapping is done in a spreadsheet by hand.
  • Customers on marketplaces receive the wrong size.
  • Stock on a marketplace falls out of step with your store.
  • Every new season means filling in templates again.

FAQ

Frequently asked questions

The questions readers ask us after this guide.

Still have a question?

Ask us directly — a senior engineer will get back to you.

Ask about your project

Which marketplaces can this work with?

Any with an API or approved connector for sellers. Zalando and ASOS Marketplace both have seller programmes; what each allows depends on your account.

Do we need a marketplace connector app?

Often you already have one for orders and stock. We add the fashion-specific mapping and validation that it lacks.

Who decides how awkward sizes map?

You do. We propose rules and show examples, and you approve them.

Are AI-drafted attributes safe to use?

Only after your team checks them. They are drafts to save typing, not final data.

What drives the cost?

The number of marketplaces and countries, and how many product types need their own mappings.

Keep reading

More on Problems We Solve

Start here

Tell us how your fashion brand runs day to day

Describe your ranges, where you sell (your own store, wholesale, marketplaces) and which spreadsheets and inboxes hold it together. We will tell you what we would build or connect, and if an app or a setting you already pay for covers it, we will say so.

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  2. A senior engineer reviews itAnd comes back with questions, a realistic range and an honest view on fit.
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