Amazon SKU: What It Is,
How to Create One & Free Generator
Your SKU is the one identifier on Amazon that you control completely. Here is how to build a system that makes inventory management, PPC reporting, and multi-channel selling significantly easier.
What Is an Amazon SKU?
SKU stands for Stock Keeping Unit, pronounced “skew.” On Amazon, it is the unique alphanumeric code you assign to each product listing in your seller account. Amazon uses it to track your inventory internally, and you see it throughout Seller Central in inventory reports, order data, and advertising dashboards.
The most important thing to understand about an Amazon SKU is that it belongs entirely to you. Unlike an ASIN, which Amazon assigns to a product, or an FNSKU, which Amazon generates for FBA labeling, the SKU is under your control. You decide the format. You decide what information it contains. And you can make it as informative or as opaque as you choose.
Customers never see your SKU. It does not appear on your listing page, in your product title, or in any customer-facing part of Amazon. It is purely an internal tracking tool. But internal tracking is exactly what separates sellers who know their numbers from those who are always guessing.
What happens if you skip it? If you leave the SKU field blank when creating a listing, Amazon auto-generates one for you. That auto-generated code looks something like this: X00234KDPL. It tells you nothing about the product, its size, its color, or its fulfillment channel. Every seller who lets Amazon generate their SKUs eventually regrets it when they try to analyze reports at scale.
A well-structured SKU, by contrast, might look like this: EBC-YOGA-MAT-PPL-6MM-FBA-001. Anyone reading it can immediately tell it is an FBA listing for a 6mm purple yoga mat from the EBC brand, and it is the first item in that product line. The information encoded in your SKU becomes searchable and filterable data across every report Amazon generates.
What a Good SKU System Actually Does for Your Business
The practical benefits go further than most articles describe.
Inventory reorder signals. When you sort your inventory by SKU, a logical naming convention lets you see at a glance which specific variant is running low. Without it, you are reading through product titles to identify what needs restocking. With it, you can build reorder rules in any spreadsheet or inventory management software based on SKU patterns rather than manually tracking individual ASINs.
Demand forecasting. Amazon’s own systems use SKU data to forecast demand at the listing level, which affects how your products are positioned in the fulfillment network. On the seller side, a consistent SKU structure lets you spot which variants trend seasonally, which ones spike after promotions, and which have steadily declining velocity, without pulling separate reports for each product.
Returns and customer service traceability. When a return comes in, the SKU on the order tells your team exactly which product, which variant, and which fulfillment batch the unit came from. For sellers managing quality issues or supplier disputes, this matters. A return traced to NVX-SPT-RESIST-BLK-MD-FBA-001 from a specific shipment batch can be investigated. A return traced to X00234KDPL tells you nothing without a lookup.
Team communication. Once your catalog grows beyond 50 products, your team, your virtual assistants, and any software integrations you use will reference SKUs constantly. A SKU that encodes product information means fewer lookup errors and faster responses when a question comes up about inventory or an order.
SKU vs ASIN vs FNSKU vs UPC
These four identifiers appear constantly in Seller Central and get mixed up constantly by new sellers. Each one does something different, and confusing them leads to real listing and labeling errors.
Seller SKU
Your internal tracking code. You set it when creating a listing. Up to 40 characters. Only visible inside your Seller Central account. Use it to encode product attributes, fulfillment channel, and sequence numbers for your own reporting.
ASIN
Amazon’s product catalog identifier. Every product in Amazon’s catalog has exactly one ASIN. Multiple sellers can share the same ASIN if they are listing the same product. The ASIN is visible on the product detail page. You do not create or own it.
FNSKU
Fulfillment Network Stock Keeping Unit. Amazon generates this automatically when you convert a listing to FBA. It ties your specific inventory to your seller account inside Amazon’s warehouses. This is the barcode you print and affix to each unit before shipping to a fulfillment center. Learn more about FNSKU codes on Amazon in our dedicated guide.
UPC / EAN / GTIN
Universal product codes issued by GS1. Amazon requires a valid UPC or EAN to create most new listings. Unlike SKUs, these codes are standardized globally and the same product carries the same UPC regardless of who sells it. See the full breakdown of GTIN vs UPC vs EAN vs FNSKU.
| Identifier | Who Creates It | Visible to Customers? | Required for Listing? | Unique To |
|---|---|---|---|---|
| Seller SKU | You | No | Yes (or Amazon generates one) | Your seller account |
| ASIN | Amazon | Yes | Yes (auto-assigned) | Amazon’s product catalog |
| FNSKU | Amazon (for FBA only) | No | Only for FBA | Your FBA inventory units |
| UPC / EAN | GS1 (purchased) | Sometimes | Usually required | Product globally |
Free Amazon SKU Generator
Fill in the fields below and the generator will build a structured SKU in real time. Choose a format that fits your catalog, then copy the result directly into Seller Central. All fields that encode attributes you actually care about will appear as labeled segments in the breakdown.
Choose a format, fill in your product details, and copy the SKU directly to Seller Central. Maximum 40 characters.
Generator tip: The Full Format encodes brand, category, product name, color, size, fulfillment channel, condition, and sequence number. Use it when your catalog has variants across multiple attributes. The Short Format drops category and condition for sellers with simpler, single-category catalogs where those fields would add length without adding useful data.
How to Build a SKU Naming Convention
There is no single right format. The format that works best depends on your business model and how you use your data. Here are worked examples for three common seller types.
Private Label Sellers
Private label catalogs tend to have multiple products, each with color and size variants. The goal is to encode enough information to identify a product and its variant without opening the listing.
Example format: [BRAND]-[CAT]-[PRODUCT]-[COLOR]-[SIZE]-[CHANNEL]-[SEQ]
Real example: NVX-SPT-RESIST-BLK-MD-FBA-001
This reads as: Novax brand, Sports category, resistance band, black, medium, FBA, first item in sequence.
Every variant of that resistance band gets its own SKU. The red medium band becomes NVX-SPT-RESIST-RED-MD-FBA-001. The black large becomes NVX-SPT-RESIST-BLK-LG-FBA-001. When you run an advertising report and sort by SKU, every variant of every product is immediately identifiable without a lookup table.
Wholesale Sellers
Wholesale sellers often deal in large numbers of products from multiple brands. Encoding the brand and category helps, but many wholesale sellers also include their purchase cost in the SKU. This lets them calculate margin on any sale by looking at the SKU without opening a separate spreadsheet.
Example format: [SUPPLIER_PREFIX]-[CAT]-[UPC_LAST4]-[CONDITION]-[COST]-[SEQ]
Real example: PKR-HMK-4821-NEW-1250-001
This reads as: Parker supplier, Home & Kitchen, UPC ending 4821, new condition, cost $12.50, first unit sequence.
The cost field (1250 representing $12.50) requires a convention your team agrees on and sticks to. Some sellers use actual dollars with a prefix: C1250. Others use a simple integer representing cents. Either works as long as it is applied consistently. When an order comes in for PKR-HMK-4821-NEW-1250-001, anyone on the team knows the margin floor for that unit without opening a spreadsheet.
Retail Arbitrage Sellers
Retail arbitrage sellers source individual units from retail stores and need to track condition, cost, and channel at the unit level. Their SKU systems tend to be simpler but include condition and cost fields prominently.
Example format: [CAT]-[ASIN_LAST4]-[CONDITION]-[COST_IN_CENTS]-[CHANNEL]-[SEQ]
Real example: TOY-B7K2-USD-899-FBA-003
This reads as: Toys category, ASIN ending B7K2, used condition, cost $8.99, FBA, third unit.
Retail arbitrage SKUs tend to be shorter because each unit may only sell once, so the convention is more about fast lookup than long-term catalog management.
Need Help With Your Amazon Catalog Strategy?
We audit SKU systems, listing structure, and inventory setups for sellers who want cleaner data and faster decision-making across their catalog.
How to Add a SKU in Seller Central
There are three ways to add or assign a SKU in Seller Central. Use the first method for single listings, the second for bulk uploads, and the third if you need to view or update existing ones.
Single Listing via Add a Product
Log into Seller Central and go to Inventory, then Add a Product. Search for your product in Amazon’s catalog or choose “I’m adding a product not sold on Amazon” for a new listing. On the product detail form, you will see a field labeled “Seller SKU.” Enter your structured SKU code here. If you leave it blank, Amazon generates one automatically. Once you submit the listing, the SKU is set and cannot be changed without deleting and relisting the product.
Bulk Upload via Inventory File
For adding multiple listings at once, download the relevant inventory file template from Seller Central under Catalog, then Add Products via Upload. The template includes a “seller-sku” column where you enter your codes for each row. This is the fastest way to assign structured SKUs to a large number of products simultaneously. It is also how most experienced sellers import new inventory from a supplier spreadsheet without manually entering each listing. If you already have live listings with Amazon-generated SKUs and want to update them in bulk, you can do so using the same flat file process: download your current inventory file, update the SKU column, and re-upload. Note that for FBA listings with active inventory, re-uploading with a changed SKU creates a new listing rather than editing the existing one, so follow the FBA SKU transition steps in Section 7.
Viewing Existing SKUs in Manage Inventory
Go to Inventory, then Manage All Inventory. Each product row shows the Seller SKU next to the listing title. You can search by SKU using the search bar at the top of the inventory page. For a full SKU export, go to Reports, then Inventory Reports, and download the Active Listings Report. This gives you a spreadsheet of every active listing with its SKU, ASIN, price, and quantity.
Amazon’s SKU Rules and Character Limits
Amazon gives sellers significant freedom in how they structure SKUs, but there are specific technical rules you need to know before building your naming convention.
Maximum 40 Characters
Amazon enforces a hard 40-character limit. The generator above tracks this in real time. Anything over 40 characters will be rejected when you submit the listing or inventory file.
Letters, Numbers, Hyphens, Underscores
These four character types are fully safe to use in any SKU. Hyphens (-) and underscores (_) are the best separators between SKU segments because they do not cause issues in spreadsheets or inventory management systems.
No Spaces
Spaces are not permitted in SKUs. They break sorting and search functions in Seller Central and cause errors in most inventory management software that reads your SKU field. Use a hyphen or underscore instead.
Avoid Ambiguous Characters
The uppercase letter O looks identical to the number 0 in many fonts. The uppercase I is indistinguishable from the number 1 or lowercase L at small sizes. Avoid these four characters in your SKUs to prevent data entry errors: O, 0, I, l.
Do Not Start With Zero
Some inventory management and accounting software interprets a leading zero as a numeric field and strips it, turning “001” into “1.” This breaks your sequence numbering and makes records harder to sort. Start sequences at 1 or use a letter prefix like “P001.”
Case Sensitivity Varies
Amazon’s system is generally not case-sensitive for SKU matching, but certain third-party integrations treat uppercase and lowercase differently. Pick one case (most sellers use all uppercase) and stick to it across your entire catalog.
Special characters: Amazon technically allows currency symbols and some punctuation in SKUs, but they are not recommended. These characters often cause problems in CSV files, inventory exports, and third-party software integrations. Stick to letters, numbers, hyphens, and underscores and you will avoid compatibility issues across every tool you ever use with your account.
Can You Change a SKU? What Actually Happens
This is the question that catches sellers off guard, often after they have already built a catalog with poorly structured SKUs and want to fix it.
For FBM listings, you can edit the SKU field in Seller Central relatively straightforwardly. Go to the listing, click Edit, and update the SKU field before saving.
For FBA listings with inventory currently at Amazon’s warehouses, the process is more involved. You cannot simply edit a SKU while units are active in the fulfillment network. Here is what you actually have to do.
Create a New Listing With the Correct SKU
Create a second listing for the same ASIN using your new, correctly structured SKU. Do not send any inventory to this new listing yet. Set it to FBA but leave the inventory level at zero.
Run Down Inventory on the Old SKU
Continue selling from your existing FBA inventory under the old SKU until stock runs low. Send your next replenishment shipment to the new listing with the correct SKU. Time this so the old inventory runs out approximately when the new shipment arrives, to avoid a stockout gap.
Switch the Old Listing to FBM With Zero Quantity
Once the old SKU’s FBA inventory is fully depleted and the new SKU’s inventory is checked in and active, convert the old listing to Fulfilled by Merchant and set quantity to zero. This deactivates it without deleting any historical data tied to that SKU in your reports.
Note: It Is a Policy Violation to Have Two Active FBA Listings for the Same ASIN
Amazon does not allow two active FBA listings for the same ASIN and condition type at the same time under the same seller account. The new SKU listing should only become active as FBA once the old one is deactivated or its FBA inventory is gone. Time the transition carefully to stay within policy.
The real lesson: The correct time to build a proper SKU system is before you send your first FBA shipment, not after you have 200 ASINs live with Amazon-generated codes. Plan your naming convention once, document it, share it with anyone who adds listings to your account, and apply it from day one. It takes 30 minutes to set up and saves dozens of hours later.
The SKU-to-PPC Connection Most Sellers Miss
Your Seller SKU appears in Amazon’s advertising reports. This is a feature most sellers never use intentionally, but it becomes genuinely useful once your SKU naming convention encodes meaningful data.
When you download a Sponsored Products report or a Search Term Report from Seller Central, the SKU field is included for every row of data. If your SKUs are structured consistently, you can filter and sort that data in ways that Amazon’s reporting interface does not offer natively.
Here are three practical examples of what this looks like in practice.
Filter by Fulfillment Channel
If your SKUs encode FBA or FBM (e.g., the segment “-FBA-” or “-FBM-“), you can filter the advertising report to show performance only for FBA products. This is useful when you run campaigns for both channels and want to analyze them separately without manually identifying which ASIN belongs to which channel.
Filter by Product Category
If your SKU includes a category code (e.g., “-SPT-” for Sports), you can filter ad spend and conversion data by category across your entire catalog in a single pivot table. This helps you see which product lines are profitable in ads without clicking through dozens of campaigns.
Track Color and Size Performance
For product lines with multiple variants, encoding color and size in the SKU lets you filter ad reports by specific variants. If the black medium consistently outperforms every other variant in ad-attributed sales, you can shift your budget toward it without guessing which ASIN corresponds to which variant.
Margin Tracking at the SKU Level
Wholesale sellers who encode purchase cost in their SKUs can pull an order report, match it against ad spend, and calculate true margin per unit without a separate database. The data is already in the SKU field of every report.
None of this requires third-party tools. It is available in the native Amazon reports. The only requirement is a consistent SKU structure that your account applies to every listing from the start.
Keeping SKUs Aligned Across Multiple Channels
If you sell the same product on Amazon, Shopify, Walmart, or any other platform, SKU alignment across those channels prevents inventory reconciliation errors and overselling.
The most common mistake multi-channel sellers make is using completely different SKU formats on each platform, because each platform was set up at a different time by a different person. The result is that the same physical product has three different identifiers across three platforms, and any inventory management software you use to sync stock levels has to maintain a manual mapping table between them.
Two approaches work well for multi-channel sellers.
Channel Suffix Approach
Keep the base SKU identical across platforms and add a channel suffix at the end:
- ✓Amazon:
NVX-SPT-RESIST-BLK-MD-FBA-001-AMZ - ✓Shopify:
NVX-SPT-RESIST-BLK-MD-FBA-001-SHP - ✓Walmart:
NVX-SPT-RESIST-BLK-MD-FBA-001-WMT
Any inventory tool that syncs across platforms can match records by the shared base segment and route stock updates correctly. The channel suffix prevents the platforms from overwriting each other’s inventory counts when they share a feed.
Shared Base SKU Approach
Use an identical SKU across all platforms and rely on your inventory management software to route channel-specific fulfillment. This is cleaner but requires that the software handles channel routing internally. It works well with tools like Linnworks, SkuVault, or Extensiv (formerly Skubana). The risk: if your software loses the channel routing mapping, the same SKU code on every platform makes it impossible to tell which platform’s data is which in a raw export.
Amazon-specific note: Amazon treats SKUs as unique per seller account, not per marketplace. If you sell in the US, UK, and EU Amazon marketplaces, Amazon assigns separate SKUs for the same product on each marketplace — even if you created them yourself using the same code. This means your US SKU NVX-SPT-RESIST-BLK-MD-FBA-001 and your UK SKU with the same code are tracked independently in each marketplace’s Seller Central. Add a country code suffix if you want to keep your data clean across marketplaces: NVX-SPT-RESIST-BLK-MD-FBA-001-US and NVX-SPT-RESIST-BLK-MD-FBA-001-UK.
Frequently Asked Questions
X002PLKM34. The listing will function normally, but the auto-generated SKU carries no meaningful information about your product. You will not be able to use it for filtering in reports, and any team member looking at your inventory list will need a separate reference document to know which code corresponds to which product. It is better to enter any structured SKU, even a basic one, than to accept Amazon’s generated code.NVX-SPT-RESIST-BLK-MD-FBA-001 in their account, there is no conflict. They are in separate accounts and Amazon tracks them independently. The uniqueness requirement only applies within a single seller account — you cannot have two active listings in your own account using the same SKU.NVX-SPT-RESIST-BLK-MD-FBA-001-US versus NVX-SPT-RESIST-BLK-MD-FBA-001-UK. This keeps your data clean if you ever merge reports from multiple marketplaces into a single analysis.