Generate EAN-13, UPC-A, Code 128, Code 39 and 11 more barcode types as SVG or print-ready PNG. Type 12 digits and the check digit is filled in; get one wrong and we name the digit it should be.
Rows that fail validation are listed with their reason in skipped.txt inside the ZIP.
A barcode that scans at retail needs a GS1-issued company prefix. This tool draws the graphic; it does not assign numbers. Internal labels need no registration.
Written and reviewed by the developers who build the Go Tools encoding utilities. The module counts, the check-digit arithmetic and the encoder behaviour described here were measured against a running engine rather than taken from other people's summaries.
Only if the number was issued to you. The image this page draws is correct and will scan, but the *number* inside it has to be allocated to you by a GS1 member organisation before a retailer's system will accept it. Making up a number that starts with a registered prefix risks colliding with a number already assigned to someone else. Internal labels — shelves, bins, assets, work orders — need no allocation; use Code 128.
Either works. The thirteenth is a check digit derived from the first twelve, so you can type either. Type 12 and it is appended and shown to you; type 13 and it is verified, with the expected digit named if it does not match.
No. 690–699 and 680–681 are the prefix ranges administered by GS1 China, and 489 Hong Kong, 471 Taiwan, 958 Macau. But GS1 states plainly that a member company may manufacture anywhere in the world and may license a prefix from the organisation of its choice, so the prefix identifies **who issued the number**, not where the goods came from.
Almost always the quiet zone or a resized image. In order of how often it is the cause: the quiet zone was clipped by a label edge or a border; the image was resized in a layout tool so a module is no longer a whole number of printer dots; the module width is simply too small for the scanner and the print resolution. All three are decided before you print, and all three are shown on this page.
A linear barcode is a run-length encoding of one string. Each character becomes a fixed pattern of bars and spaces, measured in modules — the width of the narrowest bar, written X. Code 128 spends 11 modules per symbol; a string of nine characters comes out 134 modules wide, because the total is 11 × (characters + 2) + 13: one start symbol, one check symbol, and a 13-module stop pattern.
Two things that are part of the symbol but look like empty space are where most home-made barcodes fail. The first is the quiet zone, the blank margin on each side; a scanner uses it to find the edge of the code, and a logo or a table border reaching into it makes the whole code unreadable. The second is the check digit in the retail symbologies, a single digit computed from the others that lets a scanner reject a misread instead of emitting a wrong product number.
Code 128 text = "HELLO-123" symbols = 1 (start) + 9 (data) + 1 (check) = 11 modules = 11 × 11 + 13 (stop) = 134 X = 3px = 402 px + quiet zone 10X + 10X = 462 px
Every digit with its weight, the weighted sum, and the modulo step. If you paste 13 digits and the last one is wrong, the page names the digit it should have been and offers the corrected number in one click — rather than reporting "invalid".
Not just a number in a table. The margin the specification requires is tinted on the preview, and it is asymmetric where the spec is asymmetric — EAN-13 wants 11X on the left and 7X on the right, not 10X on both.
One module at 203 dpi is 0.125 mm, at 300 dpi 0.085 mm, at 600 dpi 0.042 mm. The panel converts your chosen module width to millimetres at the resolution you select, so the printed size is a decision rather than a surprise.
Digits pair up two per symbol in subset C, so eight digits take 79 modules where character-by-character encoding would take 123 — 35.8% narrower. The readout shows which subset was used and what it saved.
EAN-13, EAN-8, UPC-A, UPC-E, ITF-14, Interleaved 2 of 5, Code 128 with its A/B/C subsets, Code 39, Code 93, Codabar, MSI and Pharmacode. Everything is drawn by JavaScript in the page; no value is sent anywhere.
Paste one value per line and get SVG or PNG files in a ZIP. Rows that fail validation are not silently dropped — they land in skipped.txt with the reason, so a batch of 100 that returns 97 files tells you which three and why.
npx bwip-js --bcid=ean13 --text=9780306406157 --scale=3 out.png A BWIPP-derived engine with by far the widest symbology coverage — over a hundred, including 2D and postal — available as a CLI and a library. Worth reaching for when barcodes are generated by a build step, or when you need symbologies this page does not cover. Note that it adds no quiet zone unless you pass paddingleft/paddingright, and that height is in millimetres, not pixels.
python -m barcode ean13 9780306406157 -o out.svg Convenient inside a Python pipeline and writes SVG by default. Covers the EAN/UPC family, Code 39 and Code 128; the more unusual symbologies and GS1 application identifiers are out of scope.
The usual choice when the same codebase has to both write and read codes. Its reader is the more famous half; for writing, the symbology coverage is narrower than BWIPP's.
Popular because it needs no tooling, and the usual source of unscannable labels. Code 39 fonts require you to add the * delimiters yourself; Code 128 fonts require you to compute the check character yourself; and a font renders at whatever size the document says, with no control over module width.
Not a generator, and not optional if the code has to work in retail. GS1 issues the number; drawing the bars is the easy part. Internal warehouse and asset labels need no allocation at all.
978030640615
9780306406157 digit 9 7 8 0 3 0 6 4 0 6 1 5 weight ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 product 9 21 8 0 3 0 6 12 0 18 1 15 sum = 93, 93 mod 10 = 3, check = (10 - 3) mod 10 = 7
The weights alternate 3 and 1 starting from the rightmost digit of the payload. Textbooks usually say "odd and even positions", which forces a different formula for each length; counting from the right gives one rule that covers EAN-13's 12 digits, UPC-A's 11 and EAN-8's 7. This particular number is the ISBN-13 of a well-known textbook, so the answer is checkable against the printed book.
9780306406158
The last digit should be 7, not 8. [ Use 9780306406157 ]
The encoder underneath refuses the number outright — it raises ean13badCheckDigit. That is correct but useless: a number copied off a package is far more likely to have one mistyped digit than to be structurally wrong, and the only thing the person needs is which digit. So validation happens before the encoder is called.
12345678
subset C: 4 symbols -> 79 modules subset B: 8 symbols -> 123 modules saving: 35.8%
Subset C encodes two digits per symbol. The module count follows 11 × symbols + 35, so halving the symbol count nearly halves the width. This is why an all-numeric internal code is worth keeping all-numeric — adding a single letter forces the whole string back to one character per symbol.
12345
12345 (5 digits) -> 79 modules 123456 (6 digits) -> 68 modules 12345678 (8 digits) -> 79 modules
Subset C cannot pair a leftover digit, so an odd-length numeric string pays for one extra switch symbol. The consequence is genuinely counter-intuitive and worth knowing before you design a numbering scheme: six digits are narrower than five, and five digits take exactly as much room as eight. Keep internal numeric codes even-length and you get the shorter barcode for free.
X = 3 modules px, printer = 203 dpi
1 dot @ 203 dpi = 0.125 mm X = 3 dot = 0.375 mm EAN-13 symbol = 95 modules + quiet 11X + 7X = 113 X = 42.4 mm
A thermal printer can only place whole dots. Exporting at 1× and printing at the same resolution keeps every module a whole number of dots. Scaling the image afterwards in a layout tool does not: the module becomes a fractional number of dots, the printer rounds each bar independently, and the bar-to-space ratio drifts until scanners start failing.
Retail products use EAN-13 (EAN-8 for small packs, UPC-A in North America). Cartons use ITF-14. Anything internal — shelf labels, asset tags, work orders — should use Code 128, which needs no registration and packs digits two per symbol.
EAN-13 takes 12 or 13 digits, UPC-A takes 11 or 12, EAN-8 takes 7 or 8. Shorter forms have their check digit appended for you. Code 128 and Code 39 take variable-length text.
Pick the module width and the resolution of the printer you will use. The panel shows what one module works out to in millimetres at that resolution. Resizing the exported image in a layout tool is what breaks scannability, so set the size here instead.
SVG stays sharp at any printed size and is what label software prefers. PNG at 2× or 4× is for places that cannot take vectors. Batch mode takes one value per line and returns a ZIP, with any rejected rows listed alongside their reason.
A 13-digit EAN-13 whose last digit does not match the other twelve is the most common real-world input. Being told which digit it should be takes one look; being told the number is invalid takes a trip to a separate calculator.
9780306406158 -> invalid EAN-13
9780306406158 -> the last digit should be 7, not 8
[ Use 9780306406157 ] Twelve digits in and thirteen out is the behaviour you want, but only if you are told about it — otherwise the number you print differs from the number in your spreadsheet and nobody knows which is authoritative.
in: 978030640615 out: barcode (13 digits, no mention)
in: 978030640615 out: barcode + "check digit 7 added automatically"
The encoder will not stop you. What comes out scans, but it does not decode to the characters you entered, and the barcode is noticeably wider than the text length suggests.
Code 128 <- 订单 (2 characters, 134 modules — same as 9 ASCII characters)
Code 128 <- ORDER-2026-0042 (ASCII, and the width matches the content)
Generators default to no margin at all. Placed against the edge of a narrow label, or inside a boxed design, the code loses the blank run a scanner needs to locate it and simply never reads.
|▐▌▐▐▌ ▐▌▐ ▌▐▐▌| <- label edge touching the bars
| ▐▌▐▐▌ ▐▌▐ ▌▐▐▌ | <- 11X left, 7X right kept blank
Resizing to a "nice" physical size makes one module a fractional number of printer dots. The printer rounds each bar independently, the bar-to-space ratio drifts, and the code degrades gradually — which is worse than failing outright, because it passes the desk test and fails in the field.
export 1x, then scale to 38 mm in the layout tool
set module width so the code is 38 mm at 300 dpi, export 1x, place at 100%
C for even-length digits, CB when an odd length forced a switch, B for anything with a non-digit.(10 - sum mod 10) mod 10. For 978030640615 the sum is 93, so the check digit is 7. This page lays the whole calculation out under the input. The same rule covers UPC-A's 11 digits, EAN-8's 7 and ITF-14's 13, because counting weights from the right makes the length irrelevant. skipped.txt with the reason, so a batch of 100 that returns 97 files tells you which three failed and why. Everything happens in the browser, so the size of the batch is limited by your machine, not by a server quota. Encoding & Formatting
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