📊 Barcode Generator

What Is a Barcode?

A barcode is just data drawn as bars. A scanner reads the widths and spacing of the bars, decodes them back into characters, and looks the value up in a database. The three formats this tool generates cover the vast majority of real-world barcode needs. Code 39 is the classic alphanumeric barcode seen on ID badges, library books, and inventory labels. Code 128 is its denser modern cousin, used in shipping labels (it is the format behind most UPS and FedEx tracking numbers), healthcare, and logistics. EAN-13 is the 13-digit retail barcode printed on nearly every product sold outside North America, and its US equivalent UPC-A is nearly identical. Each format has its own rules for which characters it can encode and how it validates the data, and this generator follows the published encoding tables for all three.

The Three Formats, Compared

When to Use Each Format

Use Code 39 when the barcode lives in a rough environment: warehouse bins, tool check-out tags, and conference badges, where an older or low-quality scanner might be used. Its wide bars and simple pattern make it the most forgiving format to print and scan. Use Code 128 when you need more data in less space: carton labels, serial numbers, order numbers, and shipping labels, where the mandatory checksum also gives you an extra layer of data integrity. Use EAN-13 only for retail products, and only with a genuine GTIN you registered with GS1. A random 13-digit number will encode and scan just fine, but no retailer or marketplace will accept it, because the number has to be globally unique to your product.

One common mistake is using a retail format for internal tracking. If the barcode never leaves your building, Code 39 or Code 128 is simpler and gives you readable letters and SKUs instead of bare digits. The human-readable text printed under the bars should always match exactly what is encoded, so a person can type it in when the scanner fails.

Printing Tips for Barcodes That Scan

Contrast is everything. Print black bars on white (or very light) paper, never reversed, and never over a colored background or pattern. Print at 300 DPI or higher: inkjet at draft quality produces fuzzy bar edges that confuse scanners. Never shrink a barcode below 80 percent of its generated size, and keep the quiet zone, the blank space on both sides, at least as wide as the tool renders it. Laminating is fine as long as the surface is matte: glossy lamination creates glare that kills scans. Finally, always test with the actual scanner you will use in production, not just your phone camera. Scan from the printed copy, at the distance you will really use, before you print a thousand labels.

Technical note: Code 39 uses the standard narrow/wide bar table with start/stop asterisks. Code 128-B uses the published 11-module pattern table with Start B, a mod-103 checksum, and the stop pattern. EAN-13 uses the standard L/G/R parity tables with guard bars and a calculated check digit.