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Free Code 128 Barcode Generator

Universal high-density barcode supporting all 128 ASCII characters.

11. Selected SymbologyISO/IEC 15417

Code 128

Code 128 — High-density alphanumeric barcode. Best for shipping labels, Amazon FNSKU & inventory.

22. Enter Barcode ValueVALID ✅

ℹ️ Full 128 ASCII character set (A-Z, a-z, 0-9, and symbols)

⚙️ Barcode Sizing & Visual Style▼

Bar Width (2x)

Bar Height (px)

Quiet Zone Margin

Text Font Size

Bar Color

Background Color

Display Human-Readable Text

Text Position

Instant Barcode Preview

Vector Live Preview

Download Format:

TECHNICAL SPECCHECKSUM PASS

TYPE: Code 128

LENGTH: 9

DATA: ABC-12345

What is Code 128 Barcode?

Universal high-density barcode supporting all 128 ASCII characters. Defined under standard ISO/IEC 15417, Code 128 is engineered for fast, reliable optical scanning across industrial and commercial environments.

Specification	Details
Standard Symbology	Code 128 (ISO/IEC 15417)
Character Set	Full 128 ASCII character set (A-Z, a-z, 0-9, and symbols)
Checksum Algorithm	Modulo 103 check digit (automatically calculated)
Quiet Zone Margin	Minimum 10 times the narrow bar width (X-dimension) on both left and right sides
Processing Mode	100% Client-Side In-Browser (Zero Server Logs)

✅ Key Advantages

•High data density with variable length
•Supports numbers, uppercase letters, lowercase letters, and punctuation
•Three auto-switching code sets (A, B, C) for maximum compression
•Universally recognized by virtually all 1D barcode scanners

📦 Common Use Cases

•Logistics, carton tracking, and container labeling
•Amazon FNSKU inventory barcode labels
•Internal asset tagging and warehouse inventory management
•Healthcare and medication sample tracking

📐Engineering Specification

Deep-Dive: How Code 128 Encodes Data

Code 128 is a compact, high-density linear symbology defined under international standard ISO/IEC 15417. It is designed to encode all 128 standard ASCII characters (values 0 through 127), spanning numeric digits, uppercase letters, lowercase letters, ASCII control codes (such as TAB, Carriage Return, and NUL), and extended punctuation. Because each character is represented by three bars and three spaces comprised of 11 module units (with a 13-module stop pattern), Code 128 provides twice the data density of legacy symbologies like Code 39.

⚙️ Three Dynamic Subsets & Auto-Switching Architecture

Code 128 dynamically optimizes string length through three complementary character subsets:

›Code Set A: Encodes all uppercase letters (A–Z), numeric digits (0–9), punctuation marks, and ASCII control characters (00 to 95), such as NUL, SOH, CR, LF.
›Code Set B: Encodes all standard uppercase (A–Z) and lowercase letters (a–z), numeric digits (0–9), ASCII symbols, and high-order ASCII characters.
›Code Set C: Encodes double-density numeric digits (00–99). Each bar-and-space symbol encodes two numeric digits simultaneously, halving the physical barcode width for numeric serial numbers and tracking codes.
›Dynamic Shift/Switch: Modern generators automatically insert Code C for long numeric sequences and switch back to Code B or A for mixed text, maximizing scanning reliability while minimizing print footprint.

🔬 Physical Barcode Anatomy & Zone Breakdown

Leading Quiet Zone

At least 10 times the narrowest bar width (X-dimension) of blank margin prevents optical scanner clipping.

Start Pattern

Designates the initial encoding set (Start A, Start B, or Start C) and sets scanner timing reference.

Encoded Data Modules

Variable-length sequence of 11-module character symbols encoding your payload.

Modulo 103 Check Character

Mandatory checksum calculated via weighted positional sums to guarantee 99.999% scan accuracy.

Stop Pattern

A standardized 13-module bar pattern (2 bars, 3 spaces terminating with a final bar).

Trailing Quiet Zone

Equal margin matching the leading quiet zone to signal completion to optical detectors.

🖨️ Production & Printing Best Practices

✔Maintain an X-dimension of at least 7.5 to 10 mils (0.19 to 0.25 mm) for standard desktop/retail scanners, and 15 to 20 mils for industrial warehouse scanning.
✔Always allow adequate quiet zones on both edges—never position the edge of the label closer than 0.25 inches (6.35 mm) to the barcode bars.
✔For Amazon FNSKU inventory labels, use 300 DPI vector rendering with human-readable text positioned beneath the bars.

📷

Optical Scanner Compatibility: Universally supported by 100% of standard 1D laser scanners, linear CCD imagers, handheld warehouse mobile computers (Zebra, Honeywell, Datalogic), and modern 2D area imagers.

Frequently Asked Questions

What is Code 128 barcode?

Code 128 is a high-density, variable-length linear (1D) barcode symbology defined by ISO/IEC 15417. It can encode all 128 ASCII characters including uppercase letters, lowercase letters, numbers, and punctuation.

How does Code 128 check digit calculation work?

Code 128 uses a Modulo 103 checksum. Each character is assigned a weighted value multiplied by its position index in the string. The sum is calculated modulo 103, and the corresponding check character is appended before the stop pattern.

Can I use Code 128 for Amazon FNSKU labels?

Yes! Amazon FNSKU barcodes use Code 128-A or Code 128-B format. MakeMyBarcode generates 100% compliant Code 128 barcodes for Amazon seller inventory.

What is the difference between Code 128 and Code 39?

Code 128 is much more compact and data-dense than Code 39. Code 128 supports lowercase letters and full ASCII with a built-in Modulo 103 checksum, whereas standard Code 39 supports only uppercase letters and digits.