# How supermarkets make sure all barcodes are unique?

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Since the barcodes are coming ftom the manufacturer how you can make sure they are all unique? With you scan a product you need to make sure it’s unique

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There are organisations like GS1 that companies register with. They give your company a unique identifier that you have to use as the start of every barcode. After that each company can put their product code. [https://www.gs1.org/](https://www.gs1.org/)

There are rules what information has to be put where.

So basically the code translates to a long number. Some digits represent the company that produced it, then some wich product of that manufacturer it is, and then there is a checksum so that wrong readings can be discovered.

There are ISO norms that regulate this. You have maybe heard about the one for books: the ISBN identifies every book with a unique number.

The ISBN always starts with 978 or 979 to show it’s an ISBN, then a single digit for region, then 5 digits for the publisher, then 3 for wich book it is and 1 digit for a checksum

[https://en.wikipedia.org/wiki/GS1](https://en.wikipedia.org/wiki/GS1)

There is an organization [see above] which coordinates the standards at all levels of the supply chain which was created for this very reason.

They buy them. There’s a place where you buy some numbers. Then you convert them into a binary code (ones and zeroes) and when you print evey zero as a black stripe and every one as a white gap than you have your barcode. The company where you buy the numbers (everybody can buy them there) takes care that they are always fresh and unique. Then you feed your computersystem in your shop with that numbers and tell: 1 is milk, 2 is butter, 3 is bread and so on. And then you tell the cash registers 1 is 0.99 \$, 2 is 0.59 \$, 3 is 1.99 \$ and so on. When the cashier scans the barcode, the price is shown and added to your bill.

In realliry the producer buys them and the whole sale, where a shop buys his stuff, provide a computer file with the product’s name and the barcode numbers and sometimes even the prices on it. At the central computer of the shop they can change the price for an offer etc.

They don’t. The barcodes used in retail stores are Universal Product Codes (UPC), and are issued by the global standards organization: [GS1](https://en.m.wikipedia.org/wiki/GS1). GS1 makes sure the UPCs are unique for currently registered items.

GS1 is the official barcode system / company .

Every brand registers and buys their barcodes there so you know if it’s unique to the brand owner and can’t be repeated

Easy, the supermarket doesn’t.

An organization named GS1 manages all the UPC barcodes and when you need one you apply for one and they assign it to you. Their job is to make sure everyone has a unique barcode.

Obviously if you’ve got people using non-GS1 barcodes you run into issues, but since that’d be a bad thing pretty much all the various industries that make consumer goods have gone with GS1. And, note, that’s worldwide. A UPC barcode in the US should correspond to exactly the same product in Japan.

Actually the answer is very simple. There is an actual central registry for bar codes. If it was left up to the individual store. The manufacturer or individual store would have make sure they put their personalized code on every package. Similar set up for qr codes.

If you have an unique 10+ digit number, and a system for converting digits to lines of varying thickness, then different numbers will produce different line patterns.