Sum of products: {sum}. Round up to the next
multiple of 10: {next}. Check digit:{' '}
{next} − {sum} = {check}
{check === given ? `, which matches the last digit of ${value}.` : `, but ${value} ends in ${given}: this number is not valid.`}
;
};
const EAN_L = ['0001101', '0011001', '0010011', '0111101', '0100011', '0110001', '0101111', '0111011', '0110111', '0001011'];
const EAN_R = EAN_L.map(p => p.replace(/./g, c => c === '0' ? '1' : '0'));
const EAN_G = EAN_R.map(p => p.split('').reverse().join(''));
const EAN_PARITY = ['LLLLLL', 'LLGLGG', 'LLGGLG', 'LLGGGL', 'LGLLGG', 'LGGLLG', 'LGGGLL', 'LGLGLG', 'LGLGGL', 'LGGLGL'];
const leftChar = k => 3 + 7 * k + 3.5;
const rightChar = (k, halfWidth) => 3 + halfWidth + 5 + 7 * k + 3.5;
const ANATOMY = {
'ean-13': {
length: 13,
quiet: [11, 7],
encode: d => {
const parity = EAN_PARITY[d[0]];
const left = d.slice(1, 7).map((n, i) => (parity[i] === 'L' ? EAN_L : EAN_G)[n]).join('');
const right = d.slice(7).map(n => EAN_R[n]).join('');
return '101' + left + '01010' + right + '101';
},
hri: i => i === 0 ? -6 : i <= 6 ? leftChar(i - 1) : rightChar(i - 7, 42),
number: [[0, 3, 'GS1 prefix', 'Which national GS1 office issued the company prefix. Not the country the product was made in.'], [3, 12, 'Company prefix and item reference', 'The brand owner’s GS1 company prefix followed by its number for this item. Where one ends and the other begins depends on the prefix length, which you can’t tell from the digits alone.'], [12, 13, 'Check digit', 'Calculated from the other 12 digits with GS1 mod-10.']],
leftNote: 'Six digits, each seven modules wide. Each digit is drawn in one of two patterns, and the combination of patterns encodes the first digit, which has no bars of its own.'
},
'upc-a': {
length: 12,
quiet: [9, 9],
encode: d => '101' + d.slice(0, 6).map(n => EAN_L[n]).join('') + '01010' + d.slice(6).map(n => EAN_R[n]).join('') + '101',
hri: i => i === 0 ? -5 : i <= 5 ? leftChar(i) : i <= 10 ? rightChar(i - 6, 42) : 95 + 5,
extended: [[3, 10], [85, 92]],
number: [[0, 11, 'Company prefix and item reference', 'The brand owner’s GS1 company prefix followed by its number for this item.'], [11, 12, 'Check digit', 'Calculated from the other 11 digits with GS1 mod-10.']],
leftNote: 'Six digits, each seven modules wide.'
},
'ean-8': {
length: 8,
quiet: [7, 7],
encode: d => '101' + d.slice(0, 4).map(n => EAN_L[n]).join('') + '01010' + d.slice(4).map(n => EAN_R[n]).join('') + '101',
hri: i => i <= 3 ? leftChar(i) : rightChar(i - 4, 28),
number: [[0, 3, 'GS1-8 prefix', 'Which national GS1 office issued the number.'], [3, 7, 'Item reference', 'Assigned by that GS1 office for this item.'], [7, 8, 'Check digit', 'Calculated from the other 7 digits with GS1 mod-10.']],
leftNote: 'Four digits, each seven modules wide.'
},
'upc-e': {
length: 8,
quiet: [9, 7],
encode: d => {
const forZero = ['GGGLLL', 'GGLGLL', 'GGLLGL', 'GGLLLG', 'GLGGLL', 'GLLGGL', 'GLLLGG', 'GLGLGL', 'GLGLLG', 'GLLGLG'][d[7]];
const parity = d[0] === 0 ? forZero : forZero.replace(/./g, c => c === 'G' ? 'L' : 'G');
return '101' + d.slice(1, 7).map((n, i) => (parity[i] === 'L' ? EAN_L : EAN_G)[n]).join('') + '010101';
},
hri: i => i === 0 ? -5 : i <= 6 ? leftChar(i - 1) : 51 + 4,
guards: () => [[0, 3], [45, 51]],
structure: () => [['Start guard', 0, 3, 'Three modules (bar, space, bar) that tell the scanner where the symbol starts and how wide one module is.'], ['Six digits', 3, 45, 'Each digit is seven modules wide and drawn in one of two patterns. The combination of patterns encodes the number system and the check digit, which have no bars of their own.'], ['End guard', 45, 51, 'Six modules that mark the end of the symbol.']],
number: [[0, 1, 'Number system', 'Always 0 or 1.'], [1, 7, 'Zero-suppressed digits', 'The company prefix and item reference with their zeros removed. The last of the six says where the zeros go back.'], [7, 8, 'Check digit', 'The check digit of the full 12-digit UPC-A.']]
}
};
ANATOMY.isbn = {
...ANATOMY['ean-13'],
number: [[0, 3, 'Prefix', '978 or 979, which mark the number as a book.'], [3, 12, 'Registration group, registrant and publication', 'The language area or country, the publisher, and the edition. Each part varies in length, which is what the hyphens in a printed ISBN show.'], [12, 13, 'Check digit', 'Calculated from the other 12 digits with GS1 mod-10.']]
};
ANATOMY.issn = {
...ANATOMY['ean-13'],
number: [[0, 3, 'Prefix', '977, which marks the number as a serial publication.'], [3, 10, 'ISSN', 'The first seven digits of the ISSN. Its own check digit is left out.'], [10, 12, 'Variant', 'Usually 00. Publishers change it for a special issue or a price change.'], [12, 13, 'Check digit', 'Calculated from the other 12 digits with GS1 mod-10.']]
};
const Anatomy = ({type, value, plain}) => {
const spec = ANATOMY[type];
const digits = String(value).split('').map(Number);
if (!spec || digits.length !== spec.length || digits.some(isNaN)) {
return
Can’t draw {type} for “{value}”.
;
}
const modules = spec.encode(digits);
const n = modules.length;
const half = (n - 11) / 2;
const guards = spec.guards ? spec.guards() : [[0, 3], [3 + half, 8 + half], [n - 3, n]];
const tall = [...guards, ...spec.extended || []];
const isTall = m => tall.some(([a, b]) => m >= a && m < b);
const M = 4;
const [qL, qR] = spec.quiet;
const x = m => (qL + m) * M;
const width = (qL + n + qR) * M;
const labelTop = plain ? 0 : 30, barTop = labelTop + 6, barH = 70, guardH = 76, hriY = barTop + guardH + 4, labelBottom = hriY + 6;
const bottomBracket = labelBottom + 8, height = plain ? labelBottom : bottomBracket + 22;
const bars = [];
for (let m = 0; m < n; m++) {
if (modules[m] !== '1') continue;
let end = m;
while (modules[end + 1] === '1') end++;
bars.push();
m = end;
}
const structure = spec.structure ? spec.structure() : [['Start guard', 0, 3, 'Three modules (bar, space, bar) that tell the scanner where the symbol starts and how wide one module is.'], ['Left half', 3, 3 + half, spec.leftNote], ['Center guard', 3 + half, 8 + half, 'Five modules that separate the two halves. Scanners decode each half on its own, then join them.'], ['Right half', 8 + half, n - 3, 'The remaining digits, each seven modules wide, always drawn from the same set of patterns.'], ['End guard', n - 3, n, 'Three modules that mark the end of the symbol.']];
const numberSegs = spec.number.map(([a, b, name, meaning]) => [name, spec.hri(a) - 3.5, spec.hri(b - 1) + 3.5, meaning]);
const legend = [...structure, ...numberSegs];
const bracket = (key, x1, x2, y, up) => {
const t = up ? y - 4 : y + 4;
return ;
};
const marker = (key, label, cx, y) => {label};
const label = <>
{}
{bars}
{digits.map((d, i) => {d})}
;
if (plain) {
return ;
}
return
{legend.map(([name, , , meaning]) =>
{name}. {meaning}
)}
;
};
const C128 = [[2, 1, 2, 2, 2, 2], [2, 2, 2, 1, 2, 2], [2, 2, 2, 2, 2, 1], [1, 2, 1, 2, 2, 3], [1, 2, 1, 3, 2, 2], [1, 3, 1, 2, 2, 2], [1, 2, 2, 2, 1, 3], [1, 2, 2, 3, 1, 2], [1, 3, 2, 2, 1, 2], [2, 2, 1, 2, 1, 3], [2, 2, 1, 3, 1, 2], [2, 3, 1, 2, 1, 2], [1, 1, 2, 2, 3, 2], [1, 2, 2, 1, 3, 2], [1, 2, 2, 2, 3, 1], [1, 1, 3, 2, 2, 2], [1, 2, 3, 1, 2, 2], [1, 2, 3, 2, 2, 1], [2, 2, 3, 2, 1, 1], [2, 2, 1, 1, 3, 2], [2, 2, 1, 2, 3, 1], [2, 1, 3, 2, 1, 2], [2, 2, 3, 1, 1, 2], [3, 1, 2, 1, 3, 1], [3, 1, 1, 2, 2, 2], [3, 2, 1, 1, 2, 2], [3, 2, 1, 2, 2, 1], [3, 1, 2, 2, 1, 2], [3, 2, 2, 1, 1, 2], [3, 2, 2, 2, 1, 1], [2, 1, 2, 1, 2, 3], [2, 1, 2, 3, 2, 1], [2, 3, 2, 1, 2, 1], [1, 1, 1, 3, 2, 3], [1, 3, 1, 1, 2, 3], [1, 3, 1, 3, 2, 1], [1, 1, 2, 3, 1, 3], [1, 3, 2, 1, 1, 3], [1, 3, 2, 3, 1, 1], [2, 1, 1, 3, 1, 3], [2, 3, 1, 1, 1, 3], [2, 3, 1, 3, 1, 1], [1, 1, 2, 1, 3, 3], [1, 1, 2, 3, 3, 1], [1, 3, 2, 1, 3, 1], [1, 1, 3, 1, 2, 3], [1, 1, 3, 3, 2, 1], [1, 3, 3, 1, 2, 1], [3, 1, 3, 1, 2, 1], [2, 1, 1, 3, 3, 1], [2, 3, 1, 1, 3, 1], [2, 1, 3, 1, 1, 3], [2, 1, 3, 3, 1, 1], [2, 1, 3, 1, 3, 1], [3, 1, 1, 1, 2, 3], [3, 1, 1, 3, 2, 1], [3, 3, 1, 1, 2, 1], [3, 1, 2, 1, 1, 3], [3, 1, 2, 3, 1, 1], [3, 3, 2, 1, 1, 1], [3, 1, 4, 1, 1, 1], [2, 2, 1, 4, 1, 1], [4, 3, 1, 1, 1, 1], [1, 1, 1, 2, 2, 4], [1, 1, 1, 4, 2, 2], [1, 2, 1, 1, 2, 4], [1, 2, 1, 4, 2, 1], [1, 4, 1, 1, 2, 2], [1, 4, 1, 2, 2, 1], [1, 1, 2, 2, 1, 4], [1, 1, 2, 4, 1, 2], [1, 2, 2, 1, 1, 4], [1, 2, 2, 4, 1, 1], [1, 4, 2, 1, 1, 2], [1, 4, 2, 2, 1, 1], [2, 4, 1, 2, 1, 1], [2, 2, 1, 1, 1, 4], [4, 1, 3, 1, 1, 1], [2, 4, 1, 1, 1, 2], [1, 3, 4, 1, 1, 1], [1, 1, 1, 2, 4, 2], [1, 2, 1, 1, 4, 2], [1, 2, 1, 2, 4, 1], [1, 1, 4, 2, 1, 2], [1, 2, 4, 1, 1, 2], [1, 2, 4, 2, 1, 1], [4, 1, 1, 2, 1, 2], [4, 2, 1, 1, 1, 2], [4, 2, 1, 2, 1, 1], [2, 1, 2, 1, 4, 1], [2, 1, 4, 1, 2, 1], [4, 1, 2, 1, 2, 1], [1, 1, 1, 1, 4, 3], [1, 1, 1, 3, 4, 1], [1, 3, 1, 1, 4, 1], [1, 1, 4, 1, 1, 3], [1, 1, 4, 3, 1, 1], [4, 1, 1, 1, 1, 3], [4, 1, 1, 3, 1, 1], [1, 1, 3, 1, 4, 1], [1, 1, 4, 1, 3, 1], [3, 1, 1, 1, 4, 1], [4, 1, 1, 1, 3, 1], [2, 1, 1, 4, 1, 2], [2, 1, 1, 2, 1, 4], [2, 1, 1, 2, 3, 2], [2, 3, 3, 1, 1, 1, 2]];
const C39_CHARS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%';
const C39 = [0x034, 0x121, 0x061, 0x160, 0x031, 0x130, 0x070, 0x025, 0x124, 0x064, 0x109, 0x049, 0x148, 0x019, 0x118, 0x058, 0x00d, 0x10c, 0x04c, 0x01c, 0x103, 0x043, 0x142, 0x013, 0x112, 0x052, 0x007, 0x106, 0x046, 0x016, 0x181, 0x0c1, 0x1c0, 0x091, 0x190, 0x0d0, 0x085, 0x184, 0x0c4, 0x0a8, 0x0a2, 0x08a, 0x02a];
const C39_STAR = 0x094;
const I25 = ['NNWWN', 'WNNNW', 'NWNNW', 'WWNNN', 'NNWNW', 'WNWNN', 'NWWNN', 'NNNWW', 'WNNWN', 'NWNWN'];
const C93 = [0x114, 0x148, 0x144, 0x142, 0x128, 0x124, 0x122, 0x150, 0x112, 0x10a, 0x1a8, 0x1a4, 0x1a2, 0x194, 0x192, 0x18a, 0x168, 0x164, 0x162, 0x134, 0x11a, 0x158, 0x14c, 0x146, 0x12c, 0x116, 0x1b4, 0x1b2, 0x1ac, 0x1a6, 0x196, 0x19a, 0x16c, 0x166, 0x136, 0x13a, 0x12e, 0x1d4, 0x1d2, 0x1ca, 0x16e, 0x176, 0x1ae, 0x126, 0x1da, 0x1d6, 0x132, 0x15e];
const code93 = text => {
const values = [...text].map(c => C39_CHARS.indexOf(c));
const weighted = (vs, max) => vs.reduceRight((acc, v, i) => acc + v * ((vs.length - 1 - i) % max + 1), 0) % 47;
const c = weighted(values, 20);
const k = weighted([...values, c], 15);
const modules = [47, ...values, c, k, 47].map(v => C93[v].toString(2).padStart(9, '0')).join('') + '1';
const widths = [];
for (let i = 0; i < modules.length; ) {
let j = i;
while (modules[j] === modules[i]) j++;
widths.push(j - i);
i = j;
}
const n = values.length;
const name = v => C39_CHARS[v] || `value ${v}`;
return {
widths,
hri: text,
segments: [['Start character', 0, 9, 'Marks the start. Scanners don’t send it.'], ['Data', 9, 9 * (n + 1), 'Each character is 9 modules: three bars and three spaces, each 1 to 4 modules wide.'], ['Check character C', 9 * (n + 1), 9 * (n + 2), `Mod-47 over the data, with weights 1 to 20. Here, ${name(c)}.`], ['Check character K', 9 * (n + 2), 9 * (n + 3), `Mod-47 over the data and C, with weights 1 to 15. Here, ${name(k)}.`], ['Stop', 9 * (n + 3), 9 * (n + 4) + 1, 'The stop character, then a single-module bar that ends the symbol.']]
};
};
const code39 = text => {
const chars = [...text];
const check = C39_CHARS[chars.reduce((sum, c) => sum + C39_CHARS.indexOf(c), 0) % 43];
const element = bits => Array.from({
length: 9
}, (_, i) => bits >> 8 - i & 1 ? 3 : 1);
const parts = [C39_STAR, ...chars.map(c => C39[C39_CHARS.indexOf(c)]), C39[C39_CHARS.indexOf(check)], C39_STAR];
const widths = [];
parts.forEach((bits, i) => {
widths.push(...element(bits));
if (i < parts.length - 1) widths.push(1);
});
const char = 16;
const n = parts.length;
return {
widths,
hri: text + check,
segments: [['Start character', 0, 15, 'An asterisk. It marks the start, and scanners don’t send it.'], ['Data', char, char * (n - 2) - 1, 'Each character is nine elements, five bars and four spaces, three of them wide. A narrow gap separates characters.'], ['Check character', char * (n - 2), char * (n - 1) - 1, `Optional. The mod-43 check for this data is ${check}.`], ['Stop character', char * (n - 1), char * n - 1, 'Another asterisk, which marks the end.']]
};
};
const code128Values = (text, gs1) => {
const digitsAt = i => {
let n = 0;
while ((/\d/).test(text[i + n] || '')) n++;
return n;
};
let set = digitsAt(0) >= 4 ? 'C' : 'B';
const values = [set === 'C' ? 105 : 104];
if (gs1) values.push(102);
for (let i = 0; i < text.length; ) {
if (text[i] === '\x1d') {
values.push(102);
i += 1;
continue;
}
if (set === 'C') {
if (digitsAt(i) >= 2) {
values.push(Number(text.slice(i, i + 2)));
i += 2;
} else {
values.push(100);
set = 'B';
}
} else if (digitsAt(i) >= 4 && digitsAt(i) % 2 === 0) {
values.push(99);
set = 'C';
} else {
values.push(text.charCodeAt(i) - 32);
i += 1;
}
}
return values;
};
const code128 = (text, gs1) => {
const data = gs1 ? gs1Text(text) : text;
const values = code128Values(data, gs1);
const check = values.reduce((sum, v, i) => sum + v * (i || 1), 0) % 103;
const widths = [...values, check, 106].flatMap(v => C128[v]);
const head = gs1 ? 22 : 11;
const end = values.length * 11;
const startSet = values[0] === 105 ? 'C' : 'B';
const startNote = startSet === 'C' ? 'The first characters are digits, packed two to a character.' : 'The first characters are text. The start code also counts toward the check.';
return {
widths,
hri: text,
segments: [[`Start code ${startSet}`, 0, 11, startNote], ...gs1 ? [['FNC1', 11, 22, 'A special character that marks the barcode as GS1-128. Scanners don’t send it as data.']] : [], ['Data', head, end, gs1 ? 'Each character is 11 modules: three bars and three spaces. Digits are packed two to a character in code set C, then a switch to code set B handles the letters.' : 'Each character is 11 modules: three bars and three spaces, each 1 to 4 modules wide.'], ['Check character', end, end + 11, `Mod-103 check, value ${check}. Scanners verify it, then drop it.`], ['Stop', end + 11, end + 24, 'Thirteen modules, ending in a final bar.']]
};
};
const itf = (digits, wide = 2.5) => {
const widths = [1, 1, 1, 1];
for (let i = 0; i < digits.length; i += 2) {
const bars = I25[digits[i]], spaces = I25[digits[i + 1]];
for (let k = 0; k < 5; k++) widths.push(bars[k] === 'W' ? wide : 1, spaces[k] === 'W' ? wide : 1);
}
widths.push(wide, 1, 1);
const pair = 2 * (3 + 2 * wide);
const end = 4 + pair * (digits.length / 2);
return {
widths,
hri: digits,
segments: [['Start', 0, 4, 'Four narrow elements: bar, space, bar, space.'], ['Digit pairs', 4, end, 'Each pair of digits shares five bars and five spaces. The first digit sets which bars are wide, the second which spaces are wide.'], ['Stop', end, end + wide + 2, 'A wide bar, a narrow space and a narrow bar.']]
};
};
const GS1_AI_NAMES = {
'00': ['SSCC', 'The serial shipping container code: an 18-digit number for one pallet or parcel.'],
'01': ['GTIN', 'The product’s 14-digit GTIN.'],
10: ['Batch or lot', 'Up to 20 characters. Variable length, so it comes last or is followed by a separator.'],
11: ['Production date', 'YYMMDD.'],
15: ['Best before date', 'YYMMDD.'],
17: ['Expiry date', 'YYMMDD.'],
21: ['Serial number', 'Up to 20 characters.'],
37: ['Count', 'How many trade items the unit contains.']
};
const LINEAR = {
'code-39': {
quiet: 10,
encode: v => code39(v)
},
'code-93': {
quiet: 10,
encode: v => code93(v)
},
'code-128': {
quiet: 10,
encode: v => code128(v, false)
},
'gs1-128': {
quiet: 10,
encode: v => code128(v, true),
numbers: hri => [...hri.matchAll(/\((\d{2,4})\)[^(]*/g)].map(m => {
const [name, meaning] = GS1_AI_NAMES[m[1]] || [`AI ${m[1]}`, ''];
return [m.index, m.index + m[0].length, `(${m[1]}) ${name}`, meaning];
})
},
'interleaved-2-of-5': {
quiet: 10,
encode: v => itf(v)
},
'itf-14': {
quiet: 10,
bearer: true,
encode: v => itf(v),
numbers: () => [[0, 1, 'Indicator digit', 'The packaging level. 1 to 8 mean a case or other grouping of the same item.'], [1, 13, 'Item number', 'Often the first 12 digits of the item’s own GTIN-13, but not always.'], [13, 14, 'Check digit', 'GS1 mod-10, calculated over all 14 digits.']]
}
};
const Linear = ({type, value, plain}) => {
const spec = LINEAR[type];
if (!spec || !value) return
;
};
export const type_0 = "ean-13"
EAN-13 is the barcode on almost every retail product sold outside North America, and every retail scanner in North America reads it too. It encodes a 13-digit GTIN (Global Trade Item Number): the number that identifies a product at checkout.
Scan or paste a barcode and see every part of it.
Generate a valid barcode from fields.
## Where you'll see it
* **Consumer products** at retail: groceries, cosmetics, household goods, packaged electronics.
* **Books and periodicals.** An [ISBN](/reference/barcode-types/isbn) is an EAN-13 starting 978 or 979, and an [ISSN](/reference/barcode-types/issn) starts 977.
* **Japan**, where it's called JAN. Japanese numbers start 45 or 49.
* **North America**, less often. Products there usually carry [UPC-A](/reference/barcode-types/upc-a), which is an EAN-13 with a leading zero left off. US and Canadian retailers have been expected to scan EAN-13 since 2005.
## Anatomy
An EAN-13 symbol is 95 modules wide, where a module is the width of the narrowest bar or space. Each digit takes 7 modules, split into two bars and two spaces.
The example uses GS1 prefix 952, which GS1 reserves for demonstrations, so it will never identify a real product.
### The first digit has no bars
Only 12 of the 13 digits have bars of their own. Each digit in the left half is drawn in one of two patterns, called L and G, and the mix of patterns across the six digits encodes the first digit. The right half always uses a third set of patterns, R.
| First digit | Left-half patterns |
| - | - |
| 0 | LLLLLL |
| 1 | LLGLGG |
| 2 | LLGGLG |
| 3 | LLGGGL |
| 4 | LGLLGG |
| 5 | LGGLLG |
| 6 | LGGGLG |
| 7 | LGLGGL |
| 8 | LGLGLG |
| 9 | LGGLGL |
A first digit of 0 means every left-half digit uses L, and those are the same bars as a UPC-A. That's why a scanner can read a UPC-A as a 13-digit EAN-13 that starts with 0.
### GS1 prefixes
The first three digits are the GS1 prefix. It tells you which national GS1 office issued the company prefix. **It does not tell you where the product was made:** a company that joined GS1 Germany uses a 400–440 prefix wherever its products are manufactured.
| Prefix | Meaning |
| - | - |
| 001–019, 030–039, 060–139 | GS1 US. These are UPC-A numbers read as EAN-13. |
| 020–029, 200–299 | Restricted circulation within a region, for example variable-weight items priced in store |
| 040–049 | Restricted circulation within a company |
| 400–440 | GS1 Germany |
| 450–459, 490–499 | GS1 Japan |
| 500–509 | GS1 UK |
| 690–699 | GS1 China |
| 952 | Demonstrations and examples |
| 977 | Serial publications ([ISSN](/reference/barcode-types/issn)) |
| 978–979 | Books (ISBN) |
GS1 publishes [the full list of prefixes](https://www.gs1.org/standards/id-keys/company-prefix).
After the GS1 prefix come the rest of the company prefix and then the item reference. Company prefixes vary in length, so you can't tell from the digits alone where the company prefix ends and the item reference begins.
### Size and quiet zones
At 100% size a module is 0.330 mm, making the symbol 37.29 mm wide including quiet zones, with 22.85 mm bars. On consumer items GS1 allows modules from 0.264 mm (80%) to 0.660 mm (200%).
The blank margins on either side are the quiet zones: at least 11 modules on the left and 7 on the right. They're part of the symbol, and artwork printed into them is a common reason for scans to fail.
## Check digit
The last digit is a check digit, calculated from the other 12 with the GS1 mod-10 algorithm. Scanners recalculate it on every read and reject any read where it doesn't match. This catches every single-digit error and most cases of two adjacent digits swapped.
To calculate it:
1. Multiply the first 12 digits alternately by 1 and 3, starting with 1.
2. Add up the results.
3. Subtract the total from the next multiple of 10. The difference is the check digit (0 if the total is already a multiple of 10).
For the example above:
UPC-A, EAN-8, ITF-14 and every other GTIN use the same algorithm. See [Check digits](/reference/check-digits).
## Variants and related types
* **[UPC-A](/reference/barcode-types/upc-a)**: 12 digits. Add a leading 0 and you get an EAN-13 with identical bars.
* **[EAN-8](/reference/barcode-types/ean-8)**: 8 digits, for packs too small for an EAN-13.
* **[ISBN](/reference/barcode-types/isbn) and [ISSN](/reference/barcode-types/issn)**: EAN-13 numbers with prefixes 978–979 and 977.
* **Add-ons**: a separate 2- or 5-digit barcode printed to the right, used for periodical issue numbers and book prices. Scanners only read it if they're set up to.
* **[ITF-14](/reference/barcode-types/itf-14)**: marks the case a product ships in. It carries a GTIN-14, which is often the item's GTIN-13 with an extra digit in front.
* **2D barcodes**: the same GTIN can be carried in a [QR code or Data Matrix](/reference/sunrise-2027), alongside or eventually instead of the EAN-13.
## Gotchas
* **Your database has 12 digits but the scan has 13.** The product carries a UPC-A. See [an extra leading zero](/reference/scan-vs-printed-number#an-extra-leading-zero).
* **The scan has extra digits on the end.** An add-on was read along with the main barcode. See [an add-on that came along](/reference/scan-vs-printed-number#an-add-on-that-came-along).
* **Prefix 20–29 numbers aren't globally unique.** Stores and regions reuse them, often with a weight or price embedded in the digits, so look them up with the retailer's rules, not in a global product database.
* **The prefix isn't the country of origin**, even though many apps present it that way.
## Scanning it in your app
EAN-13 is in the [Retail product](/reference/barcode-groups#retail-product) group, along with every other barcode that identifies a product by its GTIN, including QR Code and Data Matrix when they carry one. Most apps that scan products should enable that group, not EAN-13 on its own.
```swift theme={null}
ScanField("Product barcode", text: $gtin)
.barcodeTypes(.retailProduct)
```
If you store GTINs, normalize them to one length so that a UPC-A scan and an EAN-13 scan of the same product match. See [Normalization](/sdk/modifiers/normalization).
## Specification
* [ISO/IEC 15420:2025](https://www.iso.org/standard/84892.html): the EAN/UPC barcode specification, covering encoding, dimensions and decoding.
* [GS1 General Specifications](https://www.gs1.org/standards/barcodes-epcrfid-id-keys/gs1-general-specifications): what the numbers mean, prefixes, and size and placement rules.
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