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
;
};
Use the lowest level for codes shown on screens, a medium level for printed labels that stay clean, and the highest level, printed larger, for codes on the outside of boxes that get scraped and knocked about.
Error correction protects against damage to part of a code. It costs space, so the right level depends on how the code is likely to get damaged.
## What error correction does
2D barcodes store extra codewords, calculated with Reed–Solomon error correction, alongside the data. If part of the code is scratched, torn or covered, a scanner uses them to rebuild what's missing.
More error correction means more of the code can be lost. It also means more modules for the same data. Printed at the same size, each module gets smaller, and small modules are harder to read from a distance, on a low-resolution printer, or with a phone camera.
So high error correction only helps if you also print the code larger. Otherwise you trade damage you might get for blur you'll definitely get.
## Choosing a level
Start with where the code will live:
| Where the code lives | What goes wrong | Error correction |
| - | - | - |
| **On a screen**: mobile tickets, boarding passes, codes in an app | Glare, low brightness, a cracked screen | The least |
| **Printed and handled gently**: documents, receipts, indoor labels | Smudges, creases | Medium |
| **On packaging and cartons**: the outside of boxes, pallets, outdoor signs | Scrapes, tears, dirt, water, tape over the code | The most, printed larger |
| **With a logo over the middle** | The logo hides part of the code on purpose | The most. QR Code only. |
Then find your barcode type:
| | Least | Medium | Most |
| - | - | - | - |
| QR Code | L | M | Q or H |
| Aztec | 23% | 23% to 33% | 50% or more |
| PDF417 | Recommended minimum | Recommended minimum | 1 or 2 levels higher |
The recommended minimum for PDF417 depends on how much data the code holds. See [PDF417](/reference/barcode-types/pdf417#error-correction). Logos over the middle aren't recommended for Aztec or PDF417.
[Data Matrix](/reference/barcode-types/datamatrix) doesn't let you choose: its error correction is fixed by its size. To make one tougher, print it with larger modules and keep the quiet zone clear.
### On screens, use the least
Screens don't get scratched. The problems are glare, a dimmed display, and moiré from the camera, and they affect the whole code at once, which error correction can't fix.
Low error correction gives you fewer, larger modules at the same size on screen, which a camera reads faster and from further away. Show the code dark on light, at full brightness, with its quiet zone clear. If you send it as an image, by email, in a message or in a wallet pass, make the white margin part of the image. A transparent background takes on the app's color, and in dark mode that leaves a dark code on a dark screen with no quiet zone.
### On boxes, use the most, and print it bigger
Boxes get damaged in patches: a scrape across a corner, a puncture, a strip of tape. That's exactly what error correction repairs. Use QR level Q or H, raise PDF417 by a level or two, and use at least 50% for Aztec.
Then print the code larger, so that the extra modules don't make each one smaller. And place it where damage is least likely: away from edges, corners, folds and seams.
## See it
These are the same data at each QR Code error correction level, each with the same scratch scaled to fit. Notice that the higher levels need more modules for the same data.
**A light scratch:**
**A heavy scratch:**
**A severe scratch:**
Decoded with a standard decoder (✅ reads, ❌ doesn't):
| Scratch | L | M | Q | H |
| - | - | - | - | - |
| Light | | | | |
| Heavy | | | | |
| Severe | | | | |
Real damage is messier than a clean scratch, and scanners differ, so test your own codes the way they'll be used.
## Levels by barcode type
| Barcode type | Levels | Notes |
| - | - | - |
| [QR Code](/reference/barcode-types/qr-code) | L, M, Q, H | Recovers about 7%, 15%, 25% and 30% of the codewords |
| [Micro QR Code](/reference/barcode-types/micro-qr) | L, M, Q | The smallest size, M1, only detects errors |
| [Aztec](/reference/barcode-types/aztec) | 5% to 95% | 23% plus 3 codewords is the recommended minimum |
| [PDF417](/reference/barcode-types/pdf417) | 0 to 8 | Each level doubles the error correction codewords |
| [Data Matrix](/reference/barcode-types/datamatrix) | Fixed by size | Larger sizes have more error correction |
| [MaxiCode](/reference/barcode-types/maxicode) | Standard or enhanced | Set by the mode |
| [Han Xin](/reference/barcode-types/han-xin) | 1 to 4 | |
| [Grid Matrix](/reference/barcode-types/grid-matrix) | 1 to 5 | 10% to 50% of the capacity |
## What error correction can't fix
* **A damaged finder pattern.** Error correction protects the data, not the patterns a scanner uses to find the code. If those are gone, the scanner never gets as far as the data. QR Code has three finder patterns and Aztec has one in the center, so protect the corners or the middle accordingly.
* **A missing quiet zone.** Artwork printed right up to the code makes it hard to find, whatever the level.
* **Poor print quality everywhere.** Low contrast, smearing or blur affects every module at once.
* **Wrong data.** Error correction restores what was printed. It can't tell you the code is the wrong one.
To make your own codes at a chosen level, use the [barcode generator](/tools/generator).
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