Bar code lookup?

No, because the numbers are not unique.

Daytona

If 2 products have the same EAN barcode then it could cause havok in a supermarket, so this would surely require no duplicated numbers.

In any particular context they are unique. But some subranges are reserved for in-house use, own-brand products, etc. So two different shops might conceivably use the same number for different things.

Of the 13 digits, the first few (typically 2, but sometimes more) are a country code (50 for UK), the next few (typically five) identify the manufacturer, the last is a checksum, and the rest identify the product.

OT Trivia: The actual barcode itself (the graphic, not the number) consists of three guard bands (one either side, one in the middle) each made up of two thin black lines with a thin white between them. The middle one in addition has thin white lines around it. The middle band separates two areas in each of which 6 digits are encoded. Each digit is encoded as two white and two black stripes of various widths ranging from thin (1 unit) to thick (4 units), adding up to a 7-unit width per digit. The whole code is therefore 3+42+5+42+3 units wide. Quiz question: Since the above only accounts for the encoding of 12 digits, how do they fit in the 13th?

For items with a UPC try

Yes, they are. (With the exception of the private ranges.)

Jon

Scripsit Ronald Raygun

One of the two 6-digit groups (IIRC the left one) has two different possible encodings for each of the 10 digits. One is the mirror image of the encoding used for that digit to the right of the middle band, but at least one of those 6 digits is encoded with a "B alphabet" instead. The exact distribution of B encodings is specific to the first digit on the code. The presence of a B encoding also tells the scanner whether it is looking at the whole barcode upside down.

Perhaps the rules have changed, but I doubt it. A few years ago a company I worked for used barcodes on financial documents for processing. We used internally generated reference numbers for the barcodes. No reference was made to any central barcode registry so know one outside the organisation would have know what barcodes were being used, therefore it was perfectly possible for others to use the same barcodes.

Daytona

Here's the deal.

Anyone can print an EAN barcode with a random number, but if you produce a product that's marketed outside your own stores, and should be recognised by product scanners, the product should have its own unique GTIN (Global Trade Identifier Number).

That's comprised of a three-digit country code ("EAN-UCC prefix"), the rest nine digits are down to the national EAN representative organisations, and the final digit is a checkdigit.

In the UK, we have the country code range 500-509, and our EAN-13 barcodes have the general structure:

(I've added spaces for clarity), where MMMMM is a five-digit manufacturer code (assigned by the UK EAN authority), PPPPP is a five-digit product code (assigned by the manufacturer), and C is a single-digit checksum.

The GTIN for each product, except when it's in a private EAN-UCC range (such as 200-299 for in-store numbers), should be registered with the EAN.

So, you should never have two different products with the same non-private-range EAN barcode.

Jon

That's right. As luck would have it, there are exactly 20 different ways of combining selections from the numbers 1,2,3,4 so that they add up to 7. But half of them are mirror images of the other half, which conveniently gives you two ways (one forwards, one backwards) of representing each digit. E.g. 3211 is 0-forwards, 1123 is 0-backwards. Fortunately not a single one of the combinations is its own mirror. The right-hand group uses only forward encodings.

I think you're mistaken about "at least one" of the left group being from the backwards alphabet. That should instead be "at most five", for it is only if they were all backwards that it would be impossible to tell whether the whole code is upside down. I understand that if the 13th digit is zero, then all 12 digits are encoded forwards. If the 13th digit is non-zero, then exactly 3 of the left group are backwards.

With only 1 of the 64 possible alphabet combinations for the left group being disallowed, and only ten needed for all possible 13th digits, there is in principle extra "room" in there to encode customised information.

Scripsit Daytona

It is most likely that the barcodes you worked with was not EAN/UPC codes. For applications other than retail product identification, other standards such as code 39 are most often used, as they are more versatile; they can represent variable-length strings of digits and letters, whereas EAN is restricted to codes consisting of exactly 8,

EAN/UPC codes are supposed to be globally unique; other applications of generic barcode encodings are not.

It was not clearly stated by the original poster that his question was about EAN codes (presumably because he was not aware of that name), but this was strongly indicated by the implied assumption at the barcodes relate to specific products.