How to read a barcode

How to read a barcode in 5 steps

As explained in the article “What are the barcode” (link), the bar code are those symbols composed of parallels black lines that are found on product packaging, bottles, parcels, that if “scanned” with “barcode reader” provide a numeric or alphanumeric code.

If you are not aware of how to read a barcode, you should know that there are many free solutions that allow you to do so, as smartphone app or “pc barcode scanner”.

On this page we will look at how to recognize the two most widely used barcode: the 12-digit UPC (Universal Product Code) and the 13-digits code EAN (European Article Number).

Read Barcode UPC Code

UPC Bar codes are typically registered and used in the United States and Canada and, therefore, do not indicate a country identifier.
The UPC bar code consists of 10 middle numbers, and two numbers at the extremes of the code, the last one is the check digit:
UPC barcode

1. Lines and spaces of Barcode

Barcodes are not formed only by black lines, but also the white spaces are important.

2. Different thicknesses

The first thing we notice that the lines can have 4 differnet thicknesses.
Differnet thicknesses of lines of barcode

3. Beginning and end of the barcode

Codes begin with the code 101 (fine line black – fine line white – fine line black)
Exactly at the half of the code there is the line 01010
Codes of beginning, half and end

4. Code of each number

Each number is represented by 7 lines according to a pre-established pattern:


(The sum of the numbers is always 7 for each single code eg: 6 represented as 1114 (1 + 1 + 1 + 4 = 7)

Note also that in the second half of the barcode, the color of the lines is the opposite of the of the first part code line colors. This allows the reader will understand the correct direction of reading.

5. Example of how read barcode

So, the barcode on the under image whose two firsts digits are 0 and 1 would start with “10132112221”. Broken down this is “101-3211-2221″ where 101 marks the beginning of the barcode, 3211 marks the digit 0 and 2221 marks the digit 1.
Barcode reading

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