Codabar Generator
Self-checking numeric barcode with A-D start/stop characters; legacy use in blood banks and libraries.
How Codabar is structured
Codabar carries 16 characters — digits 0 to 9 plus the punctuation - $ : / . + — framed by a start and a stop character taken from A, B, C or D. Each character is a seven-element pattern with a fixed number of wide bars and wide spaces, which is what makes the symbology self-checking without an appended digit. The start and stop characters are consumed by the reader and do not appear in the human-readable line.
Codabar check digit
No check digit is defined or required. Applications that need one add their own digit to the payload and validate it in software, so a Codabar symbol and its check rule are a pair agreed locally — the symbology itself will accept either.
Codabar compared with Code 39
Code 39 also frames its data with start and stop characters and also covers letters, which makes it the usual replacement. ITF handles the same numeric payloads more compactly but needs an even digit count, while Codabar accepts any length within its 16-character set. Compare the Code 39 generator page for the same breakdown of structure, check digit and use cases.
Common Codabar problems
The start or stop character is missing
Codabar is invalid without a framing character at each end, and this generator enforces it. Add A, B, C or D at both ends — libraries conventionally use A, blood banks B — and keep the same pair across a label run.
Lowercase start and stop characters were entered
Only uppercase A to D are valid framers in the standard implementation. A lowercase letter is read as data and the symbol then fails validation, so uppercase the whole payload before generating.
Letters were used inside the payload
The data set is digits plus - $ : / . +, not the alphabet. An account number with a letter suffix needs that letter moved out of the symbol or a different symbology such as Code 39.
Where Codabar is used
- Blood bank bags and laboratory sample tracking
- Library cards and book borrowing slips
- Legacy airbills, photo lab envelopes and membership cards
Not sure this is the right symbology? The barcode format guide groups every supported 1D and 2D format by industry with its character set and limits.