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August 8, 2019

What Is A SKU Number & Why Do I Need One?



If you are new to online selling then you are no doubt wondering why you’re constantly being asked for your products SKU number, its ASIN number or even its ISBN number. You’ve probably spent some time googling for answers which just leaves you with more questions than before. Don’t worry, this blog will help clear things up.

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What Is The Difference Between A SKU & All The Other Codes I’m Being Asked For?

Right off the bat you’re probably confused by the sheer amount of different numbers & codes that could potentially be required for your products, try not to panic! Odds are only a few of them will be necessary before you can start selling.

What Is A SKU?

SKU is short for “Stock Keeping Unit”. The SKU has many uses including tracking inventory to help make sure stock levels are acceptable. They can also be used to keep track of a product in a warehouse; the SKU will help make finding a product much easier for those working in large warehouses used for things such as fulfilment or those in large retail stores. The SKU is also used to differentiate variations of your products, if you’re selling different types of the same products you’re going to eventually run into issues when it comes to keeping track of your products. The SKU can help you keep much better track of your variations. The term SKU is a globally known term that is personal to you.

What Is An ASIN?

ASIN is short for “Amazon Stock Identifier Number” and is unique to products listed on Amazon. It is used by Amazon in order to keep track of all of the products listed on their marketplace. You can use existing ASIN numbers to sell your products on Amazon if they already exist in Amazon’s product catalogue. If your products aren’t already on the catalogue then you will need to register your brand on Amazon and get new ASIN numbers assigned to your products. If your product is unique you will have to add it to Amazon’s product gallery and provide the products EAN or UPC code. However if it is not a unique product then you will need to find the product on Amazon’s catalogue and find the ASIN in the product details section of the product.

What Is An ISBN?

ISBN is short for “International Standard Book Number” and is used by publishers in order to track Books, Magazines and other forms of published media. These numbers are used to help the publishers track how well their media is selling and where it is selling best. In order to get an ISBN for a new piece of media you’ll likely need to approach your countries national ISBN Agency.

What Is A UPC?

UPC is short for “Universal Product Code” and the universal part is taken quite literally. Any retailer or marketplace selling a product will use the same UPC. The UPC is not just reserved for selling online, it also goes on bar-codes, so when you are scanning a product with an app on your phone then it is really the UPC that is being scanned. The code is usually made up of 12 numbers and can be broken down in to 4 parts.When you register with GS1 to get your own designated Company Code this goes into your UPC followed by each products own number. These will  help make up your products UPC.

What Is A UPC?

What Is An EAN?

EAN is short for “European Article Number”. EAN numbers are almost identical to UPC Numbers with only one slight difference: They are 13 digits long instead of 12. The extra digit is used as the country code, to help identify where a product has been manufactured.

What Is A GTIN?

GTIN is short for “Global Trade Item Number”. It is used to look up product information in databases belonging to retailers, collectors and such. A GTIN in much the same as a UPC or a EAN. If you require a GTIN for your products then you can register with GS1 here.

Why Do I Need To Know All These Codes

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The good news is you don’t, well not all of them anyways. You just need to know which platforms use which codes. So lets start by listing off each potential platform and noting which type of code they will require you to provide. It’s worth noting that some codes, such as the ISBN only being applicable to published media such as books

What Product Codes Do I Need For Amazon?

To list your products on Amazon you will need the following types of codes.

  • SKU
  • UPC/GTIN/EAN – A barcode for Amazon to identify it.
  • ASIN – Amazon will either have this created already if your product is already on Amazon. If not, you will have to create one.
  • ISBN – If your product is a book.


To list your products on Ebay you will need the following type of codes.

  • UPC/EAN/GTIN – A barcode for eBay to identify it as a legitimate product.
  • ISBN – If your product is a book.


Etsy offer you the option to use your own SKU’s. however its not a strict requirement. Etsy focus on unique products so they do not require barcodes.

  • SKU


EKM is a marketplace meaning your product requirements are a lot less strict.

  • SKU


Similar to EKM with less strict product requirements.

  • SKU


Again, another marketplace. Meaning less strict with product requirements.

  • SKU


OnBuy is a marketplace with stricter product requirements, you will need the SKU.

  • SKU
  • ISBN – If your product is a book.


That might be an awful lot of information to take in but thankfully most online platforms only require you to provide a SKU for your products. There are obviously exceptions to this such as Amazon which requires several of different types of product identifying numbers in order to upload your products, however as long as you focus on the information you do need for your chosen platforms and if you decide to expand onto other platforms you can learn those as you go.


An ideal solution for those having issues keeping track of all their different type of bar codes is to take advantage of the product management features available on OnePatch. Using the OnePatch system will help make it much clearer to you which information you need for your products & your desired selling platform. Once you’ve filled out the product requirements on OnePatch your products will be ready to upload to any of your chosen sales platforms. Sign up for a 14-day free trial now.

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