Code 93

What is a Code 93 barcode?

Code 93 is a linear barcode symbology introduced by Intermec in 1982 as a higher-density, more secure successor to Code 39. Like Code 39, it encodes 47 characters: uppercase A–Z, digits 0–9, and special characters (- . $ / + % SPACE), plus four special shift characters for Full ASCII mode. Unlike Code 39, Code 93 uses two mandatory check characters (modulo 47), making it more reliable for critical data capture applications. It is widely used in Canada Post shipping labels and some logistics and inventory systems.

Symbol structure explained

Each Code 93 character is represented by 3 bars and 3 spaces (6 elements total), each 1–4 modules wide — totalling 9 modules per character. The symbol begins with a unique start character (*) and ends with a full-width termination bar after the stop character. Two check characters (C and K) are appended before the stop character and are calculated from weighted modulo-47 sums of all preceding characters.

Dual check character algorithm (Modulo 47)

Code 93 appends two check characters:

1. Check C: Weighted sum of all data character values, with weights cycling 1,2,3…20,1,2,3… from right to left; result mod 47.
2. Check K: Weighted sum of all data characters PLUS Check C, with weights cycling 1,2,3…15 from right to left; result mod 47.

Both checks are verified by every Code 93 scanner, providing double error detection superior to Code 39's optional single check.

Code 93 vs. Code 39 vs. Code 128

Code 93 encodes the same 47-character set as Code 39 but in approximately 25% less space, due to its 6-element (vs. 9-element) character structure and lack of inter-character gaps. Code 128 is denser still and supports the full 128 ASCII set, making it the preferred choice for new designs. Code 93 occupies a niche where Code 39 compatibility is needed but space is limited.

When to use Code 93

Code 93 is the right choice when:

• Canada Post shipping label specifications require it.
• A legacy system mandates Code 93 for inventory or asset tracking.
• You need better density than Code 39 without switching to Code 128's more complex implementation.

For new designs, prefer Code 128 unless a specific standard requires Code 93.

Printing requirements

Minimum X-dimension: 0.191 mm (7.5 mil). Quiet zones: 10× X-dimension each side. No mandatory minimum height, but a height ≥ 15% of symbol width is recommended. Always include human-readable text below for manual fallback. The two check characters should appear in the human-readable line for verification purposes.

Common scanning failures

Insufficient quiet zone is the primary Code 93 failure mode. Because characters are narrower than Code 39, ink spread proportionally affects Code 93 more — a ±20% bar-width tolerance must be maintained. Always verify print quality with a calibrated barcode verifier before production runs.