Code 128 Barcode Generator

What Code 128 is

Code 128 is the general-purpose barcode of shipping and inventory. It encodes any printable ASCII text, so it carries serial numbers, SKUs, order numbers, bin locations and tracking codes that mix letters and digits. Computer Identics Corporation introduced it in 1981, and it is standardised as ISO/IEC 15417. For products sold in shops, use a UPC-A or an EAN-13 instead.

It is popular because it is dense and safe. Each character takes 11 modules, a run of digits packs two to a character, and a mandatory check character catches misreads. Courier labels, warehouse shelf and bin labels, and many hospital wristbands use it. Want the bin name rather than the code under the bars? Switch the text line to your own words in More settings, or hide it.

Code sets A, B and C

Code 128 has three character sets and can switch between them in the middle of a barcode. You do not need to pick one; the generator chooses for each part of your text whichever makes the barcode shortest.

Code set C is why a 16-digit number makes a Code 128 no wider than 8 letters. Each pair of digits takes one character instead of two, so 0123456789012345 and ABCDEFGH both come to 143 modules, 47.2 mm at X 0.33 mm. Numbers are cheap in Code 128; letters cost a full character each. A mix gains from short digit runs too: ABC-1234 is 43.6 mm because its four digits pack into two pairs.

How wide and how tall

Code 128 has no fixed size. The width depends on the text and on X, the width of the narrowest bar. The table shows real widths from this generator at X 0.33 mm, including the 10-module quiet zones on each side.

To check your own text before you design the label, type it below and read its width at three bar widths.

If a barcode is too wide for your label, lower X before you shorten the bars. X 0.25 mm is about 10 mils and exactly 2 dots on a 203 dpi printer; at 0.19 mm, the smallest this tool allows, you need a sharp printer and a good scanner. US specifications often give X in mils, and More settings switches the tool to mils or inches.

A good rule of thumb for bar height, taken from the Code 39 standard ISO/IEC 16388, is 15% of the barcode's width without its quiet zones, and at least 5 mm. That lets a scanner line cross every bar even when the label is held at an angle. On a GS1 logistics label, the GS1 General Specifications ask for 31.75 mm. Shelf-edge and bin labels often run vertically; rotate the barcode by 90° in More settings rather than turning the label file afterwards.

Printing on a label printer, and why fonts fail

Most Code 128 labels come off a thermal printer, and a thermal printer works in whole dots: 0.125 mm at 203 dpi and 0.085 mm at 300 dpi. A bar that falls between dots prints a dot too wide or too narrow. Choose Label printer under Printing on, pick your printer's dpi, and the generator snaps every bar to whole dots, for example 0.254 mm (3 dots) or 0.339 mm (4 dots) on a 300 dpi printer. Download the PNG and print it at 100%, with no scaling or fit to page.

Not sure the printer kept the size? Print test page in the download bar makes a PDF with the barcode, a 100 mm ruler and a 50 mm square. Print it at 100% and measure the ruler with a real one.

If you made the labels with a barcode font in Excel or Word, the font is the likely reason they do not scan. It draws bars for the characters you type but leaves out the start, check and stop characters that every Code 128 needs. Insert the barcode as an image instead: one PNG or SVG from here, or a whole column at once in bulk mode, as a ZIP or a label sheet.

Code 128 and GS1-128

GS1-128 is not a different barcode. It is Code 128 with an FNC1 character placed right after the start pattern, which tells the scanner that the data follows GS1 rules: numbers in brackets called Application Identifiers, each followed by a value. (01)09506000134352(17)271231(10)ABC123 carries a GTIN, an expiry date of 31 December 2027 and a batch. Pallet labels and food and pharmaceutical shipping labels use it. Older documents call it UCC-128 or EAN-128.

Use plain Code 128, as this page makes, for your own internal codes. If a customer or retailer asks for a GS1 logistics label, the data has to follow the AI rules; you can check a string with the GS1-128 parser, or a whole column of them with the GS1-128 bulk parser. For small items the same data fits in a GS1 DataMatrix on the Data Matrix page.

When a Code 128 does not scan

Besides a missing quiet zone, a font that leaves out the check character and bars that fall between printer dots, two causes are specific to the data you type.

The text has characters the generator cannot hold

Accented letters such as é, curly quotes pasted from a word processor, and emoji are not printable ASCII. The generator stops on them and names the character, so you can replace it before printing. The standard can carry accented letters through a special FNC4 character, but scanner support for it varies, so the generator keeps to plain ASCII.

The barcode is too long for the label

A 30-character Code 128 at a sensible X is wider than most labels. Shorten the data, lower X a little, or move to Data Matrix, which holds the same text in a square a few millimetres across.

Frequently asked questions