How to use it
- Type your SKU, order or asset number. Upper and lower case, digits and symbols all work.
- Set the bar width for your printer: 13 mil for most labels, 10 mil for small tags on a good printer.
- Download, or switch to Bulk / Label sheet to print many at once.
Why Code 128 is the default for internal barcodes
Code 128 can encode every character on a keyboard and squeezes runs of digits into half the space by pairing them (Code Set C). That makes it shorter than Code 39 for the same data, so it fits on small labels. It also includes a check character, so a misread is caught instead of entering the wrong SKU.
Use it for anything that stays inside your business: SKUs, bin locations, work orders, serial numbers, library cards, asset tags. You don't need GS1 or any registration. Amazon's FNSKU labels are Code 128 too.
Code sets A, B and C
Code 128 switches between three character sets. A covers upper case and control characters, B covers upper and lower case, and C packs two digits per symbol. The generator picks the shortest combination automatically, so you don't need to choose.
Keep it scannable
- Shorter is better. Every character adds width. If a value gets long, consider Data Matrix.
- Height matters. Make bars at least 0.25 in tall, or about 15% of the barcode's width, whichever is more.
- Thermal printers: at 203 DPI, choose bar widths that are whole printer dots (about 10 or 15 mil) for the crispest result.
- Keep the quiet zone of 10 bar widths empty on both sides.
Code 128 vs GS1-128
GS1-128 is Code 128 with a special start character and GS1 Application Identifiers like (01) GTIN and (10) lot. Use GS1-128 when a trading partner asks for it on cartons or pallets; use plain Code 128 for everything else.