If you’re new to selling products online, the word “barcode” gets thrown around a lot. Amazon requires one. eBay wants one. Your supplier’s products already have one. But what exactly is a barcode, how does it work, and why does it matter for your business? This beginner-friendly guide answers all of it.
What Is a Barcode?
A barcode is a machine-readable representation of data. It encodes information — usually a product identifier number — in a visual format that scanners and cameras can read instantly. Instead of typing a 12-digit number by hand, a scanner reads the barcode in milliseconds.
Barcodes are printed on product packaging, labels, and stickers. Every barcode you see at a retail store or on an Amazon package represents a unique product identifier stored in a database somewhere.
How Does a Barcode Work?
The most common barcode type you’ll encounter as a seller is the 1D (one-dimensional) barcode — the classic series of black lines and white spaces. Here’s how it works:
- Encoding: A 12 or 13-digit number is converted into a pattern of bars and spaces of varying widths. Each digit maps to a specific pattern.
- Printing: That pattern is printed on the product or its packaging as a barcode symbol.
- Scanning: A barcode scanner shines a light across the barcode. The black bars absorb light; the white spaces reflect it. This pattern of light and dark is read by the sensor.
- Decoding: The scanner converts the light pattern back into the original number.
- Lookup: That number is sent to a database (Amazon’s catalog, a store’s inventory system, etc.) which retrieves the product’s details.
The barcode itself doesn’t store product details. It stores only a number. The details live in the database that number is linked to.
1D vs 2D Barcodes: What’s the Difference?
1D Barcodes (Linear)
The classic striped barcode. Stores a single line of data — typically a 12 or 13-digit product number. Examples:
- UPC-A: 12 digits, used in North America
- EAN-13: 13 digits, used globally
- Code 128: Variable length, used in shipping and logistics
2D Barcodes (Matrix)
Square or rectangular patterns that can store much more data — including URLs, text, and complex identifiers. Examples:
- QR Code: The square barcode you scan with your phone
- DataMatrix: Used in manufacturing and healthcare
As a product seller on Amazon or eBay, you’ll almost always be dealing with UPC or EAN (1D barcodes).
Why Do Online Marketplaces Require Barcodes?
Marketplaces like Amazon and eBay manage millions of product listings. Barcodes solve three critical problems:
1. Unique Product Identification
Every product needs a globally unique identifier. Two sellers listing the same product should share the same product page, not create duplicates. Barcodes are the global standard for product identity.
2. Catalog Matching
When you enter a barcode number into a marketplace listing, the platform searches its catalog for that code. If found, it pre-fills product details, images, and descriptions.
3. Preventing Counterfeits
Barcodes traceable to GS1-registered company prefixes can be verified, making it harder for counterfeiters to list fake products using random numbers.
What Is the Difference Between a Barcode, UPC, and GTIN?
- Barcode: The visual symbol (the lines and spaces you can see)
- UPC: Universal Product Code — the 12-digit number a barcode represents in North America
- EAN: European Article Number — the 13-digit equivalent used globally
- GTIN: Global Trade Item Number — the umbrella term for all standardized product identifiers
Do I Need a Barcode for Every Product I Sell?
On most major marketplaces, yes. Amazon requires a GTIN for the vast majority of categories. eBay strongly recommends them for new products. Walmart requires them for all listings.
How Do I Get a Barcode for My Product?
- Decide how many products and variants you need to identify
- Purchase GS1-originating UPC or EAN codes from GoodUPC
- Assign one code per product variant
- Add the code to your listing and print it on your packaging or label
GoodUPC sells individual codes with no annual fees — ideal for small sellers who don’t need hundreds of barcodes. Getting started takes less than five minutes.
Ready to Get Your Barcode?
GoodUPC provides GS1-originating UPC and EAN barcodes with instant digital delivery — no annual subscription required.
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