Code 39
Code 39 is an older barcode for letters and numbers, used on car parts labels and US military shipping labels. Its text is often printed between two asterisks, which mark the start and end of the code.
Easily confused with
How to read it
Intermec developed it in 1975, Keyence’s barcode guide says. The name comes from its pattern: each character is nine bars and spaces, three of them wide. It encodes 43 characters, the digits, the capital letters A to Z, space and the symbols - . $ / + %, and the asterisk is kept for the start and stop characters; the human-readable text often shows them. Nine elements a character make it larger than other barcodes for the same data, Keyence notes. The standard is ISO/IEC 16388.
Also searched as: 3 of 9 barcode, barcode with asterisks, code 39, code39, code 3 of 9, logmars.
These pages say what each code and its parts mean under the standard that defines it. A barcode identifies an item; it doesn’t say where the item was made or whether it is genuine, and the label and the maker are the place to look for that.
Where you’ll see it
The Automotive Industry Action Group (AIAG) in the US standardised it for car parts labels, Keyence says. The US Department of Defense’s marking standard, MIL-STD-129, requires Code 39 barcodes on the military shipping label, though its latest revision recommends the 2D PDF417 code for package marking and removes Code 39 from some of its figures.
Look-alikes
A Code 128 barcode uses four bar widths and packs data more tightly, with no asterisks.
Read next
- Next in Barcodes and QR codesQR codeA QR code is a square two-dimensional barcode, read by an imaging scanner or a phone’s camera, often to open a website. The three large squares in its corners are finder patterns, which let a reader find the code and its angle; the rest is the data and its error correction.
- The same shape in Smoke and CO alarm soundsLow-frequency 520 Hz alarm (sleeping rooms)A fire alarm in a sleeping room that sounds a low buzz in place of a high-pitched beep. It is the three-beep fire alarm rhythm at 520 Hz, which NFPA 72 requires of alarms provided to wake people in sleeping areas.
More barcodes and QR codes
The same shape elsewhere
Browse symbols drawn with letters and numbers or lines.
Sources
- CODE 39 and Codabar | Basics of Barcodes, Barcode Information & Tips, KEYENCE Corporation, CODE 39
- MIL-STD-129R w/Change 2: Military Marking for Shipment and Storage, MIL-STD-129R, §5.4.2 and §5.2.2, U.S. Department of Defense (copy hosted by GSA), §1.2 changes; §2 ISO/IEC 16388; §5.2.2; §5.4.2.2
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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