Common Barcode Types Code128/EAN/UPC Comprehensive Analysis: Encoding Rules for Every Black Bar

Last week, a food-industry client brought me a bag of snacks and asked, "Are the black lines on this bag just printed randomly?"

I asked him to scan the code: his phone beeped, and ¥9.80 popped up.

He said, "That's amazing!"

I said it's not magic—every black line hides a string of numerical code. What you scan out is the essence of the price, the ID number of the product. This article won't cover barcode definitions—instead, it walks you through the encoding rules behind every black line.

1D Barcodes: Digital Codes Hidden in Black Lines

Core principle of traditional 1D barcodes (EAN, UPC, Code128, Code39, ITF-14): alternating black and white bars + numeric encoding. The width of each black bar, spacing, and width of white bars combine to form a digit, ultimately spelling out the country + manufacturer + product + check digit.

EAN-13: The 13-Digit Code

Length: 13 digits

Structure:

First 3 digits: Country code + 4-7 digits: Manufacturer code + 3-5 digits: Product code + 1 digit: Check digit
(690-695 = China) + LeXiang prefix + product number + Mod 10 checksum

Checksum algorithm (Mod 10, weight 3):

• From right to left, odd positions × 1, even positions × 3, then sum
• Sum + check digit = a multiple of 10
• Example: 6901234567890 → (0×1+9×3+8×1+7×3+...+6×3+9×1) mod 10 = 0 ✓

Module structure: Left guard 101 + 6 left-data digits + center guard 01010 + 6 right-data digits + right guard 101 + 13 characters (excluding check digit).

Application: Mandatory for retail in China.

UPC-A: The 12-Digit North American Code

Length: 12 digits

Structure:

1-digit system code + 5-digit manufacturer code + 5-digit product code + 1-digit check digit
(0 = regular) + LeXiang prefix + product number + Mod 10 checksum

Relationship with EAN-13: Adding a leading 0 to an EAN-13 makes it a UPC-A. Therefore, the same barcode can be recognized simultaneously as Chinese (EAN-13) and North American (UPC-A).

Application: Mandatory for Walmart and Amazon US.

Code128: Any ASCII Character

Length: Variable (1-48 ASCII characters)

Structure:

• Quiet zone + start character (Start A/B/C) + data + check digit + stop character + quiet zone
• 3 character sets: A (digits + uppercase + control characters), B (digits + upper/lowercase), C (double-digit compression for 00-99)
• Checksum algorithm: Mod 103 weighted (starting from 1)

Density: Stores 2-3 times more information than Code39 at the same width.

Application: Warehouse management (WMS), logistics tracking, production traceability.

Code39: The Factory Veteran Code

Length: Variable (digits + uppercase letters + 5 special characters)

Structure:

• Quiet zone + start character * + data + stop character * + quiet zone
• Each character = 9 elements (5 bars + 4 spaces), 2 wide and 6 narrow

Density: Low, but excellent compatibility (readable by any scanner).

Application: Internal factory traceability, automotive manufacturing, machining.

ITF-14: Dedicated to Cartons

Length: 14 digits

Structure:

• Left guard + 6 digits + 5 digits + right guard
• Every 5 digits = 1 group (2 thick bars + 3 thin bars)
• Check digit = Mod 10 weight 3

Features: Can be printed directly on corrugated board (tolerant of low printing precision).

Application: Outer packaging for logistics cartons.

2D Barcodes: Graphic Codes in Black Squares

1D barcodes can only store 13-30 digits, whereas 2D barcodes (QR, DataMatrix) can store hundreds of characters.

QR Code: 3 Zones + 4 Error Correction Levels

Structure:

• 3 position detection patterns (triangular positioning)
• 1 alignment pattern (bottom-right corner)
• Data area (black/white modules)
• Format information + error correction code

4 Error Correction Levels (L/M/Q/H):

• L: ~7% error correction
• M: ~15% error correction
• Q: ~25% error correction
• H: ~30% error correction

Capacity:

• Level L: max 4296 digits / 7089 characters
• Level M: max 3391 digits / 5596 characters
• Level Q: max 2420 digits / 3996 characters
• Level H: max 1852 digits / 3057 characters

DataMatrix: 2D Compact Code

Structure:

• L-shaped solid border (positioning)
• Dashed border (clock)
• Data area (black and white modules)

Features: Can be as small as 2.5mm × 2.5mm and still be readable.

Applications: PCB boards, electronic components, small medical device traceability.

Comparison Table of 7 Barcode Encodings

If you want to see QR code in practice — refer to how to make a QR code label?, or directly contact a LeXiang Packaging consultant, we'll provide barcode selection + GS1 application guidance within 24 hours.