# International Article Number

The International Article Number (also known as European Article Number or EAN) is a standard describing a barcode symbology and numbering system used in global trade to identify a specific retail product type, in a specific packaging configuration, from a specific manufacturer. The standard has been subsumed in the Global Trade Item Number standard from the GS1 organization; the same numbers can be referred to as GTINs and can be encoded in other barcode symbologies, defined by GS1. EAN barcodes are used worldwide for lookup at retail point of sale, but can also be used as numbers for other purposes such as wholesale ordering or accounting. These barcodes only represent the digits 0–9, unlike some other barcode symbologies which can represent additional characters.
The most commonly used EAN standard is the thirteen-digit EAN-13, a superset of the original 12-digit Universal Product Code (UPC-A) standard developed in 1970 by George J. Laurer. An EAN-13 number includes a 3-digit GS1 prefix (indicating country of registration or special type of product). A prefix with a first digit of "0" indicates a 12-digit UPC-A code follows. A prefix with first two digits of "45" or "49" indicates a Japanese Article Number (JAN) follows.
The less commonly used 8-digit EAN-8 barcode was introduced for use on small packages, where EAN-13 would be too large. 2-digit EAN-2 and 5-digit EAN-5 are supplemental barcodes, placed on the right-hand side of EAN-13 or UPC. These are generally used in periodicals, like magazines and books, to indicate the current year's issue number and in weighed products like food, to indicate the manufacturer's suggested retail price.

## Composition

The 13-digit EAN-13 number consists of four components:
* GS1 prefix – 3 digits
* Manufacturer code – variable length
* Product code – variable length
* Check digit

### GS1 prefix

The first three digits of the EAN-13 (GS1 Prefix) usually identify the GS1 Member Organization which the manufacturer has joined (not necessarily where the product is actually made). Note that EAN-13 codes beginning with 0 are actually 12-digit UPC codes with prepended 0 digit. In recent years, more products sold by retailers outside the United States and Canada have been using EAN-13 codes beginning with 0, since they were generated by GS1-US.
The 020-029 GS1 Prefixes are worth a special mention. GS1 defines this as being available for retailer internal use (or internal use by other types of business). Some retailers use this for proprietary (own brand or unbranded) products, although many retailers obtain their own manufacturer's code for their own brands. Other retailers use at least part of this prefix for products which are packaged in store, for example, items weighed and served over a counter for a customer. In these cases, the barcode may encode a price, quantity or weight along with a product identifier – in a retailer defined way. The product identifier may be one assigned by the Produce Electronic Identification Board (PEIB) or may be retailer assigned. Retailers who have historically used UPC barcodes tend to use GS1 prefixes starting with "02" for store-packaged products.
The EAN "country code" 978 (and later 979) has been allocated since the 1980s to reserve a Unique Country Code (UCC) prefix for EAN identifiers of published books, regardless of country of origin, so that the EAN space can catalog books by ISBNs rather than maintaining a redundant parallel numbering system. This is informally known as "Bookland". The prefix 979 with first digit 0 is used for International Standard Music Number (ISMN) and the prefix 977 indicates International Standard Serial Number (ISSN).

### Manufacturer code

The manufacturer code is a unique code assigned to each manufacturer by the numbering authority indicated by the GS1 Prefix. All products produced by a given company will use the same manufacturer code. EAN-13 uses what are called "variable-length manufacturer codes". Assigning fixed-length 5-digit manufacturer codes, as the UCC has done until recently, means that each manufacturer can have up to 99,999 product codes.(9,999 for 3 digit GS1 prefix's) Many manufacturers do not have that many products, which means hundreds or even thousands of potential product codes are being wasted on manufacturers that only have a few products. Thus if a potential manufacturer knows that it is only going to produce a few products, EAN-13 may issue it a longer manufacturer code, leaving less space for the product code. This results in more efficient use of the available manufacturer and product codes.
In ISBN and ISSN, this component is used to identify the language in which the publication was issued and managed by a transnational agency covering several countries, or to identify the country where the legal deposits are made by a publisher registered with a national agency, and it is further subdivided any allocating subblocks for publishers; many countries have several prefixes allocated in the ISSN and ISBN registries.

### Product code

The product code is assigned by the manufacturer. The product code immediately follows manufacturer code. The total length of manufacturer code plus product code should be 9 or 10 digits depending on the length of country code (2–3 digits).
In ISBN, ISMN and ISSN, it uniquely identifies the publication from the same publisher; it should be used and allocated by the registered publisher in order to avoid creating gaps; however it happens that a registered book or serial never gets published and sold.

### Check digit

The check digit is an additional digit, used to verify that a barcode has been scanned correctly. It is computed modulo 10, where the weights in the checksum calculation alternate 3 and 1. In particular, since the weights are relatively prime to 10, the EAN-13 system will detect all single digit errors. It also recognizes 90% of transposition errors (all cases, where the difference between adjacent digits is not 5).

## Calculation of checksum digit

The checksum is calculated as sum of products – taking an alternating weight value (3 or 1) times the value of each data digit. The checksum digit is the digit which must be added to this checksum to get a number divisible by 10 (i.e. the additive inverse of the checksum, modulo 10). See ISBN-13 check digit calculation for a more extensive description and algorithm. The Global Location Number (GLN) also uses the same method.

### Position – weight

The weight at a specific position in the EAN code is alternating (3 or 1) in a way, that the final data digit has a weight of 3 (and thus the check digit has a weight of 1).
All Global Trade Item Number (GTIN) and Serial Shipping Container Code (SSCC) codes meet the next rule:
Numbering the positions from the right (code aligned to the right), the odd data digits are always weight of 3 and the even data digits are always weight of 1, regardless of the length of the code.
Weights for 18-digit SSCC code and GTINs (GTIN-8, GTIN-12, GTIN-13, GTIN-14):
| position | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
| weight | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 |
Weights for EAN-13 code:
| position | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
| weight | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 |
Weights for EAN-8 code:
| position | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
| weight | 3 | 1 | 3 | 1 | 3 | 1 | 3 |

### Calculation examples

* For EAN-13 barcode 400638133393x, where x is the unknown check digit, (Stabilo Point 88 Art. No. 88/57), the check digit calculation is:
       position 121110987654321 first 12 digits of barcode 400638133393 weight 131313131313 partial sum 40018324193999 checksum 89
       The nearest multiple of 10 that is equal to or higher than the checksum, is 90. Subtract them: 90 - 89 = 1, which is the check digit x of the barcode.
* For EAN-8 barcode 7351353x, where x is the unknown check digit, the check digit calculation is:
       position 7654321 first 7 digits of barcode 7351353 weight 3131313 partial sum 213151959 checksum 63
       The nearest multiple of 10 that is equal to or higher than the checksum, is 70. Subtract them: 70 - 63 = 7, which is the check digit x of the barcode.

## Binary encoding of data digits into EAN-13 barcode

The GTIN numbers, encoded to UPC-A, EAN-8 and EAN-13, all use similar encoding. The encoded data is usually repeated in plain text below the barcode.

### Barcode structure

The barcode consists of 95 areas (also called modules) of equal width. Each area can be either white (represented here as 0) or black (represented as 1). From left to right:
* 3 areas for the start marker (101)
* 42 areas (seven per digit) to encode digits 2–7, and to encode digit 1 indirectly, as described in the following section
* 5 areas for the center marker (01010)
* 42 areas (seven per digit) to encode digits 8–13
* 3 areas for the end marker (101)

### Encoding of the digits

To encode the 13-digit EAN-13 number, the digits are split into 3 groups; the first digit, the first group of 6 and the last group of 6. The first group of 6 is encoded using a pattern whereby each digit has two possible encodings, one of which has even parity (denoted with letter G) and one of which has odd parity (denoted with letter L). The first digit is not represented directly by a pattern of bars and spaces, but is encoded indirectly, by selecting a pattern of choices between these two encodings for the first group of 6 digits, according to the table below. All digits in the last group of 6 digits are encoded using a single pattern RRRRRR, the one also used for UPC.
If the first digit is zero, all digits in the first group of 6 are encoded using the pattern LLLLLL used for UPC; therefore, a UPC barcode is also an EAN-13 barcode with the first digit set to zero.
Structure of EAN-13 :
| First digit | First group of 6 digits | Last group of 6 digits |
| 0 | LLLLLL | RRRRRR |
| 1 | LLGLGG | RRRRRR |
| 2 | LLGGLG | RRRRRR |
| 3 | LLGGGL | RRRRRR |
| 4 | LGLLGG | RRRRRR |
| 5 | LGGLLG | RRRRRR |
| 6 | LGGGLL | RRRRRR |
| 7 | LGLGLG | RRRRRR |
| 8 | LGLGGL | RRRRRR |
| 9 | LGGLGL | RRRRRR |
This encoding guarantees that the first group always starts with an L-code, which has odd parity, and that the second group always starts with an R-code, which has even parity. Thus, it does not matter whether the barcode is scanned from the left or from the right, as the scanning software can use this parity to identify the start and end of the code.
EAN-8 barcodes encode all digits directly, using this scheme:
Structure of EAN-8 :
| First group of 4 digits | Last group of 4 digits |
| LLLL | RRRR |
Encoding of the digits :
| Digit | L-code | G-code | R-code |
| 0 | 0001101 | 0100111 | 1110010 |
| 1 | 0011001 | 0110011 | 1100110 |
| 2 | 0010011 | 0011011 | 1101100 |
| 3 | 0111101 | 0100001 | 1000010 |
| 4 | 0100011 | 0011101 | 1011100 |
| 5 | 0110001 | 0111001 | 1001110 |
| 6 | 0101111 | 0000101 | 1010000 |
| 7 | 0111011 | 0010001 | 1000100 |
| 8 | 0110111 | 0001001 | 1001000 |
| 9 | 0001011 | 0010111 | 1110100 |
Note: Entries in the R-column are bitwise complements (logical operator: negation) of the respective entries in the L-column. Entries in the G-column are the entries in the R-column in reverse bit order. See pictures of all codes against a colored background.
A run of one or more black areas is known as a "bar", and a run of one or more white areas is known as a "space". As can be seen in the table, each digit's encoding comprises two bars and two spaces, and the maximum width of a bar or space is four areas.

### EAN-13 barcode example

* C1, C3: Start/end marker.
* C2: Marker for the center of the barcode.
* 6 digits in the left group: 003994.
* 6 digits in the right group (the last digit is the check digit): 155486.
* A digit is encoded in seven areas, by two black bars and two white spaces. Each black bar or white space can have a width between 1 and 4 areas.
* Parity for the digits from left and right group: OEOOEE EEEEEE (O = Odd parity, E = Even parity).
* The first digit in the EAN code: the combination of parities of the digits in the left group indirectly encodes the first digit 4.
The complete EAN-13 code is thus: 4 003994 155486.

### Decoding

By utilizing the barcode's center marker, a scanner can decode an International Article Number (EAN) by scanning one half of the barcode at a time through a helical scan at a 45-degree angle. This method reconstructs the full code from partial scans, useful when the barcode is obscured or damaged. Error detection algorithms, such as checksum verification, play a crucial role by identifying and correcting scanning errors, ensuring accurate decoding. Additionally, modern scanners often employ omnidirectional scanning, enhancing their ability to read barcodes at various angles.
These scanners also leverage the symmetrical structure of EAN-13, allowing decoding from either direction. Error detection algorithms, like the Luhn algorithm, commonly used in checksum calculations, verify the integrity of the data scanned. If errors are detected, the scanner can either alert the user or attempt correction, improving the reliability of scanning in dynamic or less-than-ideal conditions.

## Japanese Article Number

Japanese Article Number (JAN) is a barcode standard compatible with the EAN. It is a subset of EAN. Use of the JAN standard began in 1978. Originally, JAN was issued a flag code (EAN's number system) of 49. In 1992, JAN was newly issued an additional flag code of 45. In January 2001 the manufacturer code changed to 7 digits (9 digits including the flag code) for new companies.