Free Code 128B Barcode Generator — Full Printable ASCII Encoding
Generate Code 128B barcodes online for free. Code 128B encodes the complete printable ASCII range — uppercase and lowercase letters (A–Z, a–z), digits (0–9), and all standard punctuation characters. The most versatile Code 128 subset for mixed-case text, product descriptions, and URLs. Download as PNG or SVG instantly. No signup, no watermarks, no limits.
What Is Code 128B?
Code 128B is the most widely used encoding subset of Code 128. It covers the full printable ASCII range from 0x20 (space) to 0x7F (DEL), including all 26 uppercase letters, all 26 lowercase letters, all 10 digits, and the complete set of printable punctuation and symbols. Standardized within ISO/IEC 15417, Code 128B is the default subset assumed by most Code 128 implementations and is the correct choice for encoding any human-readable alphanumeric string that does not require ASCII control characters. If your data contains lowercase letters, Code 128B is required — neither Code 128A nor Code 128C can encode them.
- Complete Printable ASCII — Upper, Lower, Digits, SymbolsCode 128B encodes every printable ASCII character: uppercase A–Z, lowercase a–z, digits 0–9, space, and all printable punctuation and special characters including !, @, #, $, %, ^, &, *, (, ), -, _, +, =, [, ], {, }, |, ;, :, ', ", ,, ., <, >, ?, /, \, `. This is the broadest character set among the three Code 128 subsets, making Code 128B the universal choice for mixed-case alphanumeric data.
- Required for Lowercase Letter EncodingCode 128B is the only Code 128 subset that can encode lowercase letters (a–z) as standard symbol characters without mode-switch overhead. If your barcode data includes any lowercase character — product names, URLs, reference codes with lowercase letters — Code 128B is the required subset. Code 128 auto mode automatically uses Subset B for lowercase characters, but Code 128B locks the entire barcode to Subset B encoding.
- Ideal for Mixed-Case Text and Human-Readable LabelsCode 128B is the preferred format for labels where the encoded string is also displayed as human-readable text beneath the barcode. Mixed-case encoding allows product descriptions, reference numbers with lowercase suffixes, and URL paths to be encoded exactly as they appear in your system — preserving case sensitivity for applications that require it.
- Automatic Mod 103 Check CharacterCode 128B includes the standard Mod 103 check character computed and appended automatically by the encoder. The check character ensures that any single character substitution or barcode damage is detected and rejected by the scanner before the corrupted data reaches the host application.
Code 128B specifications
Code 128 locked to code set B — the full printable ASCII range including lowercase letters. The table below lists the exact Code 128B specifications — character set, check digit, X-dimension, quiet zone and the governing ISO/IEC 15417 standard — so you can size and print the symbol correctly the first time.
| Character set | Full printable ASCII 32-127: digits, upper and lowercase letters, punctuation, and space |
|---|---|
| Data length | Variable; no fixed minimum or maximum |
| Check digit | Mandatory Mod 103 check character, appended automatically |
| Density | ≈12 characters per inch at the minimum 0.19 mm X-dimension |
| X-dimension (module width) | 0.19-0.50 mm typical |
| Quiet zone | 10X on each side |
| Magnification | Scales linearly with the chosen X-dimension |
| Bar / space ratio | Variable-width bars and spaces |
| Standard | ISO/IEC 15417 |
| Introduced | 1981 — Ted Williams, Computer Identics |
Typical uses: Mixed-case alphanumeric identifiers; License keys and serial numbers with letters; General labeling where control characters never occur.
How Code 128B compares to similar barcode types
Choosing the wrong symbology is the most common cause of barcodes that scan in the warehouse but get rejected downstream. This table compares Code 128B with the formats most often confused with it, on the three properties that decide compatibility: character set, check digit, and quiet zone.
| Symbology | Character set | Check digit | Quiet zone |
|---|---|---|---|
| Code 128B(this page) | Full printable ASCII 32-127: digits, upper and lowercase letters, punctuation, and space | Mandatory Mod 103 check character, appended automatically | 10X on each side |
| Code 128 | All 128 ASCII characters: 0-9, A-Z, a-z, punctuation, and control characters (code set dependent) | Mandatory Mod 103 check character, calculated automatically by the encoder | 10X on each side (minimum 2.5 mm recommended for general scanning) |
| Code 128A | Digits 0-9, uppercase A-Z, ASCII control characters (NUL-US), and - . / : + % $ space (ASCII 0-63) | Mandatory Mod 103 check character, appended automatically | 10X on each side |
| Code 128C | Digit pairs 00-99 only (numeric data) | Mandatory Mod 103 check character, appended automatically | 10X on each side |
Code 128B Barcode Generator Features
Create production-grade Code 128B barcodes with full printable ASCII support, precise size control, and flexible download options.
Full Printable ASCII Input
Enter any combination of printable ASCII characters — upper and lowercase letters, digits, punctuation, symbols — up to any practical length. The encoder uses strict Subset B encoding for every character. Characters outside the printable ASCII range (control characters 0x00–0x1F) are flagged as invalid for Subset B.
Case-Sensitive Encoding
Code 128B preserves case exactly as entered. 'Hello' and 'HELLO' produce different barcodes with different bar patterns. This is essential for applications where the encoded value is case-sensitive — URL paths, mixed-case serial numbers, or reference codes that include both uppercase and lowercase components.
PNG and SVG Download
Download as a high-resolution PNG for use in documents, label software, and email, or as an SVG for print-ready, resolution-independent output. SVG Code 128B barcodes embed cleanly into HTML pages, PDF templates, and vector design files at any scale.
Adjustable Dimensions and Appearance
Control bar height, X-dimension, font size, and quiet zone width. Toggle the human-readable text display on or off. Change bar and background colors for custom label stock while maintaining sufficient contrast for reliable scanning. All changes reflect immediately in the live preview.
Bulk Code 128B Generation
Generate a large batch of Code 128B barcodes from a list of mixed-case values in one operation. Useful for creating serialized product labels, library book barcodes, and reference ID stickers from a spreadsheet or database export.
Code 128B — Frequently Asked Questions
Answers to the most common technical questions about Code 128B character support, differences from other subsets, and best practices.
What is the difference between Code 128B and Code 128 auto?
Code 128B locks every character to Subset B encoding. Code 128 auto dynamically switches between subsets A, B, and C within a single barcode to produce the most compact symbol. For input that consists entirely of printable ASCII characters (no control characters, no long numeric-only runs), Code 128 auto defaults to Subset B anyway and produces an identical barcode. Use Code 128B when a specification requires locked Subset B encoding or when you want to guarantee no subset switching occurs.
Can Code 128B encode control characters?
No. ASCII control characters (0x00–0x1F) are outside the Subset B character range. To encode control characters, use Code 128A or Code 128 auto mode (which can switch to Subset A when a control character is encountered).
Is Code 128B compatible with all barcode scanners?
Yes. Code 128B uses the standard Code 128 symbology defined in ISO/IEC 15417, which is supported by virtually all modern 1D barcode scanners — including laser, CCD, and imager-based scanners from all major manufacturers. The Subset B start character in the barcode tells the scanner which encoding table to use for decoding.
Does Code 128B have a maximum length?
There is no hard maximum length defined by the standard. Practical limits are set by the available physical width on your label — each character adds approximately 11 modules to the barcode width plus start, stop, and check character symbols. For very long strings, consider breaking the data across multiple barcodes or using a 2D barcode such as Data Matrix or PDF417 instead.
Specification reference
Read the full Code 128B specification — character set, check digit, quiet zone, density, and the governing ISO/IEC 15417 standard — in our barcode glossary.
Code 128B specificationRelated barcode types
Compare Code 128B with similar symbologies, or open their full specifications.
- Code 128
A high-density, variable-length linear barcode that encodes all 128 ASCII characters, and the backbone symbology of modern logistics.
- Code 128A
Code 128 locked to code set A — uppercase letters, digits, and ASCII control characters.
- Code 128C
Code 128 locked to code set C — digit pairs packed two per character for maximum numeric density.
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Generate Your Code 128B Barcode Now — Free, Instant, No Signup
Create Code 128B barcodes for mixed-case text, product references, and alphanumeric labels right now. Enter your data, customize the size, and download as PNG or SVG — completely free with no account required.