The Code 39 (3 of 9) Barcode Guide

What is Code 39?

Code 39 (also known formally as 3 of 9 barcode or Alpha39) is one of the oldest and most widely adopted alphanumeric barcodes in the world. Originally developed in 1974, it remains a pillar in non-retail industries.

It is heavily preferred for internal equipment tracking, military logistics (such as the US Department of Defense LOGMARS standard), and permanent metal asset tags. This preference is largely due to its incredibly robust structure, wide error tolerance on older scanning equipment, and the fact that it doesn't strictly require a complex checksum digit for basic operations.

Code 39 Asset Tag Generator

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Start and Stop Asterisks

A defining characteristic of Code 39 is that every valid barcode must begin and end with an asterisk (*) character.

These characters serve as mandatory start and stop symbols. They instruct the hardware scanner when to begin interpreting data and when the scan is complete, allowing the barcode to be read perfectly even if scanned upside-down. Our visual generators automatically append these characters for you to ensure compliant printing.

Discrete Character Set

Code 39 is known as a "discrete" symbology. This means each encoded character is structurally independent and separated from the next by a small physical white space (the intercharacter gap). It natively supports exactly 43 standard characters without requiring complex shift modes:

• Uppercase Letters: A through Z.
• Digits: 0 through 9.
• Symbols: Space, Dash (-), Period (.), Dollar ($), Slash (/), Plus (+), Percent (%).