Code 39 Barcode Generator (3 of 9)

What is Code 39 Barcode Generator?

Code 39, also called 3 of 9, is a variable-length alphanumeric barcode dating from 1975. Every character is made of nine elements, five bars and four spaces, and three of the nine are wide, which explains the name. The character set has 43 entries: digits 0–9, capital letters A–Z, space and the symbols - . $ / + %. A separate asterisk marks the start and end of every symbol and cannot be part of the data. Lowercase letters are not part of the standard set.

Code 39 needs no licence, no registration and no fixed length, which is why it is common in automotive labelling (AIAG), US defence logistics (LOGMARS), healthcare labelling (HIBC), ID badges and asset tags. Its weakness is density: characters are wide and separated by small gaps, so the same value needs more room than in Code 128, which packs digit pairs together and covers the whole ASCII range. Choose Code 39 when the receiving system or standard asks for it, and Code 128 when space matters.

When should you use it?

• A customer, standard or legacy system specifies Code 39 for labels, for example on automotive or defence supply parts.
• You need badge, library-card or asset-tag numbers that mix letters and digits.
• You print on low-resolution printers, where wide and simple bars are more forgiving than a dense code.
• You want to test that a scanner is set up for Code 39 and for its optional check character.

The optional mod-43 check character

Each character has a value: 0–9 are 0–9, A–Z are 10–35, then - is 36, . is 37, space is 38, $ is 39, / is 40, + is 41 and % is 42. Add up the values of the data, divide by 43, and the remainder is the value of the check character, printed just before the stop asterisk. Example: CODE39 gives 12 + 24 + 13 + 14 + 3 + 9 = 75; 75 mod 43 = 32, which is W, so the symbol encodes CODE39W. The check is optional, and the reader must be configured to expect it.

Privacy

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Your text stays in the page: the barcode is drawn locally, and it contains exactly the characters you typed plus the start/stop asterisks.