Code 39 Barcode Generator for Badges, Parts and Assets

Where Code 39 is still used

Code 39 was developed in 1974 and became one of the first alphanumeric barcodes. Each character is made of nine elements (five bars and four spaces), three of which are wide, which is where the name "3 of 9" comes from. It is self-checking, so a single printing defect cannot turn one character into another.

It is less compact than Code 128, but it remains written into many standards, including the US Department of Defense LOGMARS standard and automotive industry AIAG labels. It is also common on employee ID badges, library cards and older asset management systems.

Code 39 vs Code 128

Practical tips

• If your software does not specifically require Code 39, Code 128 will give you a shorter barcode.
• The asterisk (*) is reserved as the start and stop character, so it cannot appear inside your data.
• Keep at least 10 bar widths of quiet zone on each side, or a minimum of about 6 mm.
• Test with your actual scanner. Some older devices need Code 39 enabled in their settings.

Why Code 39 needs more space

A Code 39 character occupies nine elements - five bars and four spaces - of which exactly three are printed wide and the rest narrow, followed by a narrow inter-character gap. Nothing is shared between characters, so a damaged area costs one character rather than the whole run. The price is length: because every character pays for its own spacing, the same value takes roughly twice the label width that Code 128 needs.

The plain alphabet is 43 characters plus the asterisk that frames the symbol. Lower-case letters only exist through Extended Code 39, which encodes them as pairs such as $A for a. A reader that is not configured for the extension hands back the pair, so test with the hardware that will actually be used.