WIKI: Understanding Barcodes - UPC vs. Amazon FNSKU


Note: There is another option called an EAN. It is similar to a UPC, so throughout this article, I’ll only refer to UPC codes, which are more common. For the purpose of this tutorial, they can be used interchangeably.

The first thing to understand is that both a UPC and an FNSKU are really just a series of characters (numbers and letters) used as a unique identifier for a product. Both can be represented as a simple set of characters, or visually represented as a barcode.

So, let’s take a look at a real example: The Webkinz Sweetheart Pup with Trading Cards

The UPC code for this product is

UPC: 045635434868

As I mentioned, this series of numbers can also be represented visually as a barcode so it can be scanned with a barcode reader. This makes it easy for a product to be identified for retail use and related logistics. The barcode for this product is below, and you likely see something similar every day:

(UPC Barcode)

For our purposes, an FNSKU code isn’t really any different than a UPC code except that it’s unique to Amazon. This is what an FNSKU code might look like:

(FNSKU Barcode)

So, keep these basic descriptions in mind, but let’s take a step back for a second.

When you create a listing on Amazon for a product that doesn’t already exist in their catalog, they need a way to uniquely identify that product. Since UPC codes are universally accepted in retail, it’s required to have one when you list a product.

Now, it doesn’t matter whether you’re listing an existing branded product, or a brand new private label product that you created. Either way, a UPC number is required to create a new listing. For this purpose all you need is the number, not the barcode.

Remember, that’s the difference between:

UPC: 045635434868 (UPC Number)


(UPC Barcode)

Note: If you want to sell an item that already exists on Amazon, you won’t need to add the UPC code yourself, since the seller who created the original listing will have included it at that time.

Once you’ve create a listing on Amazon, they will assign their own unique identifier, called an FNSKU (Fulfillment Network Stock Keeping Unit). While the UPC code helps Amazon keep track of millions of different products to be used on their site, the FNSKU helps them keep track of inventory for different sellers in their fulfillment centers. So a single product will have a unique UPC code, but if 3 different sellers are offering that same product for sale on Amazon, they will each have their own unique FNSKU so Amazon can keep track of inventory between all these sellers.

To put it another way, let’s use the Webkinz Sweetheart Pup with Trading Cards example again. The UPC code for this product is 045635434868, and that won’t ever change. However, if we have three sellers for this product, Amazon will have to keep track of their inventory separately, so they will each be assigned a unique FNSKU code for that particular product.

This is why when you list an item for sale on Amazon, there will be a UPC (unique to the product) and an FNSKU (unique to the seller for that product).

So, now you might be wondering when you need each one and which should be placed on your product. This is actually where the decision of whether or not to use the Stickerless Commingled Inventory option comes in to play, so I’d recommend you read through my wiki article on the subject: Stickerless Commingled vs. Stickered Inventory.

This post is part of the Ultimate Wiki Project

The Ultimate Wiki Project: Selling on Amazon FAQ

Excellent post Dax. Is it possible to have my designer put both UPC and FNSKU on the packaging so I may save money on labelling fees?


@Keelan, No, you definitely don’t want both a UPC code and an FNSKU code showing. This will confuse Amazon.

I recommend just using the FNSKU code, but refer to this article for a better understanding:


Thanks Dax, I just need a little bit more clarification. Am I correct in thinking that I don’t need to have the supplier put anything else on the product or the unit packaging only the Label that willl go on the shipping container?


The product packaging itself will need either a UPC code or FNSKU code. Shipping labels are needed in addition to this.


Hi Dax-
I had the UPC code printed on the label of the product that is inside the box. It looks like I would need the FNSKU code from Amazon, which will cost me 20 cents per box. The reason I had it in the bottle instead of the box is because I had the impression that only the FNSKU is needed by Amazon and I did not want the UPC code to be in the way.
So for future packaging updates, I will make sure that the UPC code is printed on the box/packaging and not on the bottle that I have inside.
Also, currently, I only have the UPC CODE and no Bar Codes. Would this be an issue and if so, how do I get the barcode for my UPC Code. The code was a benefit for being an ASMer.
Thanks and blessings- Diana



On the same subject, is the UPC Code or Barcode being scanned at the Amazon warehouse for the management of the product or is this only necessary when listing the product. My concern is that the UPC code that I have is in the bottle that is inside the box. Thanks for your reply.



@Dianavc, my recommendation is to print your FNSKU code on the packaging. It should be as simple as that.


Just starting an FBA business. Sorry but this post is confusing. I don’t understand still if we need BOTH a UPC Code and FNSKU code on the packaging?


@ssigal ,

You don’t need both. You can use one or the other.

P.S. If you can let me know what part of the post was confusing, I’ll edit it to try and make it more clear for others.


hey great info dax!

was just wondering:

if i get my manufacturer to make my own private label of 1 product and i plan to sell 500 units of that product, it will still have 1 UPC code correct?
my manufacturer is based in china and will have them ship to FBA so im wondering if this is the correct process in steps:

  1. have the manufacturer create a upc code unique to the product
  2. have them ship the product to FBA location in the states
  3. FBA will take care of the rest
  4. FBA will then be able to track inventory even though none of the units have a bar code on it

please let me know if this is correct as i dont wont to do anything stupid.



#4 is not correct. You must have either a UPC code or a FNSKU code on your product before it gets to FBA.

Sorry if that’s not clear - I’m happy to update the post if any particular part seems confusing.

As mentioned above, you can send inventory to Amazon with EITHER a UPC or FNSKU, but I generally recommend just using the FNSKU. With that in mind, this would be the process:

  1. Assign a UPC code to your product listing in Amazon.
  2. Go to your Manage Inventory page and click on the down arrow next to the Edit button for your product. You’ll see an option to Print Item Label. Click on that and you’ll have the option to save a PDF of the FNKSU code. This is what I send to my supplier to add on the packaging (or apply a sticker).
  3. Have them ship product to FBA location in the states.
  4. FBA will take care of the rest.

The process would be a little different if you wanted to use a UPC code instead, so let me know if that’s what you’d intend to do.


Wow this is some great info thanks jax!

So I need to create a listing for my item even before I send the units to fba.

After telling my supplier to create a UPC code for me I assign this UPC code to my item listed (or I can create a upc on my own correct?) which I don’t need to have them label it on my product

From here I follow your instructions on getting the fnksu number and have the supplier apply a sticker for each unit on my product (on label of each unit)

Also if I were to create a UPC code wouldn’t it be easier to get the supplier to apply a UPC code on the label as opposed to the fnksu number? Would like to know why specifically I would have them create a UPC code and then have them put on a fnksu number on each unit

Appreciate your help jax!


You don’t “create” a UPC code. You can purchase one online and just assign the number to your product.

The only reason you need a UPC code is because Amazon requires that every product has a unique identifier. So, even though it’s not printed on your packaging, you can’t create a new product listing on Amazon without one.

While the UPC code is specific to a PRODUCT only, the FNSKU code is specific to the PRODUCT AND SELLER. Your supplier doesn’t have to know what your UPC code is at all. So, from their perspective it shouldn’t be any easier to print the UPC code instead of the FNSKU (or vice versa). Either way, they will just be printing whatever barcode you give them.

I have a couple of recommended places to buy UPC codes here:


Hi Dax - Great answer BTW. Question: If I have my FNSKU printed on my package and someone else (hijacker) slaps their own FNSKU on it, can I claim that they’re selling a fraudulent item? Thanks.



Not exactly. In order to claim someone is selling a different item, it probably goes without saying that the products actually have to be different.

Another seller using their own FNSKU doesn’t mean anything by itself. All the FNSKU does is help Amazon keep track of which units of inventory were sent in by which seller. In other words, assume you and another seller are both selling the Webkinz Pup in the post example. Inventory from you and another seller might be exactly the same, but different FNSKU’s help Amazon know which units of inventory came from you and which came from the other seller.

However, this is only true for sellers that have elected to the disable Stickerless Commingled setting from their account. If both you and the other seller have enabled Stickerless Commingled, Amazon won’t differentiate between the inventory that was sent in.

Conversely, disabling Stickerless Commingled ensures that your inventory won’t get mixed up with that of another seller. So, for us as private sellers, this is important if you want to purchase something from a hijacker to ensure that they don’t have an genuine copy of your product. If it’s different, you can then contact Amazon to try and get the removed from the listing.

I know this is really confusing, so I hope the response made sense. Let me know if anything isn’t clear.


Thanks for your reply Dax. I do appreciate it.

Now I’m not sure if it’s still related to the topic per se but if another seller is selling my product (that they’ve purchased from me) using their own FNSKU, then technically the product is not ‘new’ then right? Can they claim it’s ‘brand new - unopened packaged’? As ‘new’ implies that all warranties and bonuses by the manufacturer (me) are valid when I obviously won’t offer in the case of a hijacker?


It would still be considered a brand new product, but the question would be whether or not it’s different than what you are currently selling. If they are not exactly the same, the other seller should create a new listing/ASIN to sell the product.

The question about your warranty depends on the terms you outlined. I think it’s reasonable to say that the warranty is valid only if purchased from an authorized retailer (you), but you’d probably want that to be made clear wherever the terms are posted. If it’s not explicitly mentioned, I think the expectation is that a customer should be entitled to the warranty if they purchased it new, regardless of who it was from. I’m not an attorney, but that’s how I view it.

I don’t know what other bonuses you bundle with the product, but you can make the claim that it’s a different product if the other seller doesn’t provide them.

That being said, Amazon doesn’t always enforce their own rules consistently. Sometimes they take action and sometimes they don’t.


Thanks Dax. Appreciate your time in replying to this.


Hi Dax,

Great articles! I have a quick question as I am planing to start selling bracelets on Amazon, and my bracelets will be of different color and size.
Will all models but of different size have the same FNSKU?
Please advise.

Thank you.