Barcode guides
Practical guides on barcodes: which symbology to use, how check digits work, why a code will not scan, and how to print labels that do.
- Code 128 subsets, FNC1-FNC4, and the mod-103 check digit
Full reference for Code 128 covering subsets A, B and C, FNC1 through FNC4, the mod-103 check digit with a worked example, and the FNC4 Latin-1 extension. Sourced against ISO/IEC 15417:2007.
- EAN-13 structure and parity: how 13 digits fit in a 12-position symbol
The 95-module EAN-13 envelope, the L/G/R encoding tables, and the parity scheme that encodes the 13th digit without printing it. Includes the full G-code table, the left-half parity-pattern lookup, a worked decode of 5901234123457, and how the GS1 prefix system is assigned.
- UPC-A complete reference: encoding, check digit, UPC-E, and the dead variants
The 12-digit UPC-A symbol explained from modules to mod-10 check digit. Full L and R encoding tables, UPC-E zero-suppression rules with worked example, the UPC-B/C/D variants nobody uses, and where the GS1 prefix system came from.
- GS1 DataBar Explained: When It Replaces UPC and Why
The seven DataBar variants, where each one is used, and when DataBar beats UPC-A.
- Do You Actually Need to Buy UPC Codes from GS1?
Free vs paid UPCs, why cheap resold codes fail on Amazon and Walmart, and when a $5 UPC is fine.
- Code 39 vs Code 93 vs Code 128: The 1D Showdown
Three industrial 1D symbologies, one usually wins. Density, character set, check digits, and when to pick each.
- PDF417 vs Data Matrix vs QR: Picking a 2D Symbology
A practical three-way comparison of PDF417, Data Matrix and QR, covering capacity, scan hardware, use cases, and how to choose.
- ITF-14 Explained: Shipping Carton Barcodes, GTIN-14, and SSCC-18
What ITF-14 is, how it differs from GS1-128 and SSCC-18, and the size and bearer-bar rules a case label must meet to scan.
- QR Code Size: How Small Can You Actually Go?
The real math on QR code size, scan distance, and error correction - with a practical rule of thumb and the mistakes that make small codes unscannable.
- How to Print Barcode Labels That Actually Scan
DPI, X-dimension, quiet zone, and the handful of print settings that decide whether your label works. A practical guide for anyone printing labels at real volume.
- UPC vs EAN: Which One Do You Actually Need?
UPC-A and EAN-13 are the same standard with a different digit count. How to pick one, and the few cases where the choice matters.
- GS1-128 vs Code 128: Stop Confusing Them
GS1-128 and Code 128 look identical but mean very different things. Here is the difference, when each one is required, and which generator to use.
- Code 128 vs Code 39: Why Modern Retail Moved On
A technical comparison of Code 128 and Code 39 barcodes, covering character sets, density, check digits, and when each is the right choice. Code 39 survives on legacy mandates, and Code 128 wins everywhere else.
- How the EAN-13 Check Digit Is Calculated (With a Worked Example)
A complete walkthrough of the EAN-13 check digit algorithm, a worked example with a real barcode, why the check digit exists, and how the same algorithm underlies UPC-A, ISBN-13, and every GTIN format.
- Amazon FBA Barcodes: FNSKU vs UPC, and When to Use Which
A practical guide to Amazon FBA barcode requirements - what FNSKU and UPC are, how Amazon's 2026 policy change affects sellers, and how to decide which label goes on your products.
- QR Code vs Data Matrix: Which 2D Barcode Should You Actually Use?
A practical comparison of QR Code and Data Matrix barcodes. Capacity, error correction, physical size, regulatory requirements, and the one question that decides it, which is who does the scanning.
- Why Won't My Barcode Scan? A 7-Step Checklist
A checklist for diagnosing barcode scan failures, covering quiet zones, contrast, print resolution, physical damage, wrong symbology, check digits, and scanner distance.