Code 128 B Barcode Generator

What Is a Code 128 B Barcode?

Code 128 B is the character-set-B variant of Code 128, supporting the full printable ASCII range: uppercase letters, lowercase letters, digits 0–9, and standard punctuation and symbols. It does not include the non-printable control characters that subset A supports. In practice, subset B is the most commonly used of the three Code 128 subsets because most real-world data — product names, mixed-case model numbers, email-derived codes, alphanumeric order IDs — needs both letter cases in the same string.

When you use plain, auto-mode Code 128 and type any lowercase letter, the encoder will typically drop into subset B automatically to represent it. Choosing Code 128 B explicitly in Barcode Mint forces that subset for the entire symbol, which is useful when a downstream system or scanner configuration expects consistent subset B output rather than a barcode that could switch subsets mid-stream.

How Subset B Fits the Code 128 Family

All three Code 128 subsets share identical bar geometry, start/stop codes, and a modulo-103 check digit — they differ only in which characters map to which internal code values:

• Subset A — uppercase, digits, symbols, and control characters. No lowercase.
• Subset B (this page) — uppercase and lowercase letters, digits, and symbols. No control characters. The default choice for general text.
• Subset C — digit pairs only, doubling numeric density but unable to encode any letters.

Because subset B covers essentially all printable characters people actually type, it's the default assumption for anything that isn't strictly numeric or strictly control-character-driven. If your data is a long pure-digit string, subset C will produce a noticeably shorter barcode for the same information — but the moment even one letter appears, subset B (or auto Code 128) becomes necessary.

Where Code 128 B Is Used

Subset B is the default for most modern Code 128 applications involving readable, mixed-case data:

• Retail product labeling where SKUs mix letters and numbers, e.g. internal catalog codes like "SkuAb-4471".
• Order and fulfillment tracking numbers that combine carrier prefixes with alphanumeric IDs.
• Name badges and access credentials encoding a person's name or username alongside an ID number.
• Library and document management systems using mixed-case catalog or file references.
• Software license keys and serial numbers that include both letter cases for compactness.
• Marketing and coupon codes where mixed-case strings are shorter and easier to read than all-uppercase equivalents.

Code 128 B Technical Specifications

Code 128 B is governed by the same ISO/IEC 15417 standard as the other Code 128 subsets. It encodes all 95 printable ASCII characters — uppercase and lowercase letters, digits, punctuation, and symbols — but excludes non-printable control characters. Each character uses 11 modules split across 3 bars and 3 spaces, plus a distinct stop pattern at the end of the symbol. There's no fixed maximum data length in the standard itself, though physical label width and scanner depth-of-field impose practical limits. A single check digit is mandatory, computed as a modulo-103 weighted checksum over the start character and every encoded symbol value; Barcode Mint calculates and appends it automatically, so no manual math is required.

How to Create a Code 128 B Barcode in Barcode Mint

Select Code 128 B from Barcode Mint's symbology list to force subset B encoding. Type your mixed-case text or alphanumeric string into the data field — the live preview renders instantly so you can confirm the bar pattern before exporting. From there:

• Set bar width to control overall barcode length — subset B's density is the same as A and roughly half that of subset C for numeric data.
• Adjust height and font size for the human-readable line beneath the bars, keeping mixed-case text legible at your intended print size.
• Customize colors to match label branding, ensuring sufficient contrast for reliable scans.
• Verify the quiet zone margin is intact — cropping it during design work is a common cause of scan failures.
• Export as PNG, SVG, or PDF, or use Copy to embed directly into another document or design tool.

For sequential IDs — like incrementing order numbers with a letter prefix — use the batch/sequence feature. For larger label runs, the bulk CSV → ZIP/PDF tool converts a spreadsheet column into a complete set of barcode files or a single printable PDF. Developers can generate Code 128 B barcodes programmatically via the REST API using /barcode?type=code128b&data=YOURDATA.

Print and Scan Best Practices

Subset B's mixed-case flexibility comes with a few practical considerations at print time:

• Keep the printed bar width consistent with your scanner's resolution capability — thermal printers at lower DPI settings can blur adjacent narrow bars, especially at smaller label sizes.
• Maintain a quiet zone of at least 10x the narrowest bar width on both sides; this matters just as much for subset B as any other Code 128 variant.
• If your data mixes case with numbers, double-check that no unintended switch to subset C occurs if you're relying on an auto-encoder elsewhere in your pipeline — locking to subset B guarantees consistent behavior.
• Enable human-readable text for any workflow involving manual verification or re-entry, since mixed-case strings are harder to guess correctly than all-caps or all-numeric ones if a scan fails.
• Test barcode legibility against your actual print substrate — glossy label stock can introduce glare that affects scan reliability more than the character set does.

Code 128 B vs. Related Codes

Against Code 128 A, subset B adds lowercase letters but drops support for control characters — the right trade for almost all consumer-facing and general business data. Against Code 128 C, subset B is roughly twice as wide for purely numeric strings, since C encodes two digits per character; if your data turns out to be all-digit, switching to C shortens the barcode meaningfully. Against Code 39, subset B is denser and includes lowercase letters that Code 39 can't represent without its Full ASCII extension, though Code 39 remains more universally supported on very old scanner hardware. For most modern mixed-case applications, subset B (or auto Code 128) is the default recommendation over any of these alternatives.

Common uses

• Retail SKUs and catalog codes with mixed-case letters and numbers
• Order and fulfillment tracking numbers
• Employee badges and access credentials
• Library and document management catalog codes
• Software license keys and serial numbers
• Marketing and coupon codes using mixed-case strings

Frequently asked questions

Related barcode types

Browse all 106 barcode & QR types →