Barcode Generator

How to generate a barcode

1. Pick the symbology that matches your use case.
2. Type or paste the data. The hint under the field states the accepted characters and length.
3. Read the status line — it confirms the appended or verified check digit, or explains exactly what is wrong with the input.
4. Adjust bar width and height if the barcode has to fit a specific label size.
5. Download SVG or PNG, or copy the SVG markup straight into your template.

Choosing a symbology

If a retail product is involved, the numbering scheme decides the symbology for you: a GTIN-13 has to be an EAN-13 and a GTIN-12 has to be a UPC-A. For anything internal, Code 128 is usually the right default because it encodes letters, digits, and punctuation in a compact symbol.

How check digits work

EAN-13, EAN-8, UPC-A, and ITF-14 all share one check digit formula. Working from the rightmost data digit toward the left, digits are weighted 3, 1, 3, 1, and so on. The weighted sum is then subtracted from the next multiple of ten:

check = (10 - (weighted sum mod 10)) mod 10

For the data 590123412345 the weighted sum is 83, so the check digit is 7 and the complete EAN-13 is 5901234123457. Code 128 carries its own modulo-103 check symbol, which is computed and embedded automatically and never shown in the human-readable text. Code 39 has an optional modulo-43 check character that some closed systems require; enable it only when the receiving system asks for it, because a scanner that does not expect it will report the extra character as part of the data.

Printing so it scans

Two settings decide whether a printed barcode survives contact with a real scanner. The first is bar width: the narrowest bar has to stay wide enough for the printer’s resolution, so thermal labels usually want at least two pixels per module at the size you export. The second is the quiet zone — the blank margin on each side. This generator includes the quiet zone in the exported image, so do not crop the whitespace and do not place the barcode flush against a box edge or another graphic.

Bar height matters less to decoding than width, but a taller symbol is easier to scan at an angle. Keep the human-readable text switched on for anything a person may need to key in by hand when a label is damaged.

Length is the third constraint, and it only applies to the variable-length symbologies. A handheld scanner reads what fits in its field of view, so a very long payload produces a symbol that is physically valid yet unreadable in one pass. The status line flags this above 48 characters for Code 128 and above 43 for Code 39 and Codabar. The barcode is still generated — the warning tells you it needs a wider-field scanner or a shorter payload.

Scope

The seven symbologies above are what this tool encodes. UPC-E is not among them: it is the zero-suppressed print variant of UPC-A, and a scanner expands it back to the same twelve-digit number, so generate the UPC-A instead. EAN two-digit and five-digit add-ons, which carry magazine issue numbers and book prices, are separate supplemental symbols and are out of scope. Code 128 encodes your input literally — GS1-128 application identifiers written in parentheses are treated as ordinary characters rather than parsed, and no FNC1 separator is inserted. For bulk generation, run your list through a barcode library in a local script.

Privacy

Everything happens client-side. ZeroTool has no upload endpoint for this tool: the symbology tables, check digit maths, SVG rendering, and PNG conversion all execute in your browser. Your last input is kept in local browser storage so the page restores it on your next visit, and Reset clears that entry.