Barcode Generator

Bars, widths and the digit that protects the scan

A 1D barcode encodes data in the relative widths of the dark bars and light spaces. Each symbology has its table: Code 128 uses three character sets to cover the full printable ASCII range densely, while EAN and UPC have fixed patterns for the digits 0–9. The scanner does not 'read numbers' directly, it measures the sequence of widths and translates it back into characters.

In retail codes, the last digit is a check digit: it is computed from the previous ones by a weighted sum with alternating weights of 1 and 3, reduced modulo 10. If a digit is misread, the math doesn't add up and the scanner rejects the read. That is why the tool asks for the numeric base (12 digits for EAN-13, for example) and computes the final digit for you, or validates the full code if you already provide all of them.

• Data becomes patterns of bars and spaces of varying widths.
• Code 128: dense, covers the full printable ASCII range.
• EAN/UPC: numeric, with a weighted mod-10 check digit.
• Output as SVG (vector), which scales without losing sharpness.

An internal SKU and a retail EAN

Example 1, internal label: choose Code 128 and type something like 'PROD-2026-A17'. Since Code 128 accepts letters, numbers and ASCII symbols (up to 80 characters), it produces a compact code perfect for inventory, logistics and asset tracking, where you control both the printing and the scanner.

Example 2, retail product: choose EAN-13 and enter the first 12 digits; the tool computes and appends the 13th check digit automatically. If you paste all 13 digits, it validates whether the check digit matches. The same applies to EAN-8 (7→8) and UPC-A (11→12).

Great for prototypes, not enough for commercial registration

The tool is great for prototyping, testing scanners, building internal labels and generating simple artwork. It validates structure and checksum locally, but does not query GS1, retailers or external databases, inventing an EAN here does not create a real registered product. Retail codes depend on issuance and registration in the appropriate ecosystem.

To print for real, respect three things that make a code fail when ignored: high contrast (dark bars on a light background), adequate scale (not too small) and the quiet zone, the mandatory blank margin before and after the bars, without which the scanner confuses where the code starts and ends. Always test with the real scanner before printing batches.