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Programming · Cheatsheet

Barcode Formats Cheatsheet

Code 128, Code 39, EAN and UPC inputs, check digits, export settings, and print checks for barcode generation.

40 commands 8 sections

On this sheet

Formats supported by FindUtils 5 Example inputs and outputs 5 GS1 check-digit calculation 5 Input checks 5 Browser exports and limits 5 Checks before a print batch 5 What an accepted value does not prove 5 Sources and related guide 5
Try it in the browser Generate barcodes in Code128 and Code39 formats. Open Barcode Generator

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Formats supported by FindUtils

  • CODE128 Code 128 subset B: printable ASCII. No GS1-128 structure.
  • CODE39 Letters become uppercase. Supports digits, spaces, and -.$/+%.
  • EAN13 12 data digits, or 13 digits including a correct check digit.
  • EAN8 7 data digits, or 8 digits including a correct check digit.
  • UPC UPC-A: 11 data digits, or 12 digits including a correct check digit.

Example inputs and outputs

  • SHELF-A17 Code 128 preserves this supported ASCII value.
  • shelf-a17 → SHELF-A17 Code 39 converts letters to uppercase.
  • 590123412345 → 5901234123457 EAN-13 appends 7. Demonstration value only.
  • 9638507 → 96385074 EAN-8 appends 4. Demonstration value only.
  • 03600029145 → 036000291452 UPC-A preserves the leading zero and appends 2. Demonstration value only.

GS1 check-digit calculation

  • Remove the final check digit For a complete code, calculate from its data digits only.
  • 3, 1, 3, 1, ... from the right Apply weights from the rightmost data digit.
  • sum(digit × weight) Add all weighted data digits.
  • (10 - (sum % 10)) % 10 The result is one digit from 0 to 9.
  • sum = 83 → check = 7 For 590123412345, the total with the check digit is 90.

Input checks

  • Keep identifiers as text Numeric conversion can remove leading zeroes.
  • Retail formats: digits only Do not include spaces, separators, or letters in EAN and UPC input.
  • Use the supported character set Code 128 and Code 39 can omit unsupported characters from the bars.
  • Code 39: no surrounding asterisks The encoder adds its own start and stop characters.
  • 5901234123458 → error For this EAN-13 input, the correct final digit is 7.

Browser exports and limits

  • PNG Raster download. Enlarging a small image can blur its edges.
  • SVG Vector download. Final print dimensions still need a check.
  • Bar width: 1–5 px Browser slider range. REST and MCP accept 1–10.
  • Bar height: 50–200 px Browser slider range. REST and MCP accept 20–500.
  • Side margin: 20 px Fixed margin. It does not guarantee the required quiet zone.

Checks before a print batch

  • Black bars on white Start with this color combination. Check the final print requirements.
  • Keep the quiet zones clear The required blank margins depend on the barcode format and module width.
  • Print at the final size Check a sample from the actual printer and label material.
  • Compare scanner output Read the entire value. Include leading zeroes and the check digit.
  • Check the selected product Confirm that the receiving software selects the intended record.

What an accepted value does not prove

  • Product assignment A generated image does not assign a GS1 identifier.
  • Product identity A correct check digit does not establish the owner or product.
  • Every typing error Some changes to multiple digits preserve the check digit.
  • Retail print quality One successful scan does not replace the required quality verification.
  • GS1-128 support Ordinary Code 128 lacks the required FNC1 start structure.

Sources and related guide

  • https://www.gs1.org/services/how-calculate-check-digit-manually GS1: check-digit weights and calculation.
  • https://www.gs1.org/services/verified-by-gs1 GS1: identifier, company, and product information.
  • https://gs1.se/en/guides/how-to-guides/size-guide/ GS1 Sweden: barcode sizes and quiet zones.
  • https://support.gs1.org/support/solutions/articles/43000734455-what-is-the-format-of-gs1-128- GS1: the required GS1-128 start structure.
  • https://findutils.com/guides/barcode-generator-guide/ FindUtils: the full generation and export guide, dated September 6, 2026.

Related cheatsheets

  • JavaScript ES6+59 commands
  • Python Essentials59 commands
  • Regular Expressions44 commands

Guides that use these commands

  • How to Generate Barcodes: Code 128, EAN and UPCGuide · 7 min read

Tools for this work

  • Barcode GeneratorGenerate barcodes in Code128 and Code39 formats.

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