条形码入门与打印指南：Code128 / EAN-13 怎么选

Choosing: Internal Assets vs Retail

The first question isn't "which is better" but who will scan this barcode. Only your own systems, or external ones too (retail POS, marketplaces, libraries)? The answer decides the symbology.

Code128: the workhorse for internal systems

Code128 supports upper/lowercase letters, digits, and all ASCII symbols with virtually unlimited length — mixing "ABC-00123" in one code is fine. High density and reliable checks make it the de-facto standard for warehouse asset tags, work orders, membership numbers, serials, and call numbers. For internal use, pick it by default.

EAN-13: the global passport for retail

EAN-13 is a fixed 13-digit, numeric-only retail code with a worldwide structure: prefix (region) + manufacturer code + item reference + 1 check digit. It presumes a GS1 manufacturer prefix — a self-made "EAN-13" without one is not a legitimate retail code and won't be accepted by proper retail channels.

Once you've picked a type, generate it with this site's Barcode Generator — choose the symbology, type the content, and the check digit is computed automatically, all locally in your browser.

How Check Digits Work

A check digit is a self-test digit at the end of the code: the scanner decodes each bar, recomputes the checksum, and rejects the result on mismatch. It guards against misreads — smudges, faded ink, and skew that flip a digit are mostly caught by the check.

The EAN-13 mod-10 algorithm

Take the first 12 digits, weight them alternately 3 and 1 from the right, sum them, then: check digit = (10 − last digit of the sum) mod 10. A worked example:

First 12:  6 9 0 1 2 3 4 5 6 7 8 9
Weights:  ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3
        = 6 +27 +0 +3 +2 +9 +4 +15 +6 +21 +8 +27
        = 128 → last digit 8 → check = (10−8) mod 10 = 2
Full code: 6901234567892

Generators compute it for you, but knowing the mechanics pays off twice: you can spot a mistyped digit on a printed label, and when a "perfectly printed" code won't scan, a wrong check digit is a prime suspect.

Code128's built-in check

Code128's check isn't a visible character — every symbol carries a mod-103 check character appended automatically at encode time. Nothing to manage; just know that shorter, wider codes read right on the first pass more often.

Print Specs: Size, Resolution, Quiet Zone

Barcodes are hard-edged graphics — fine on screen, fragile in print. Three hard requirements:

• Minimum size: EAN-13 standard size is 37.29×25.93 mm with a minimum magnification of 80%; Code128 narrow elements should stay above 0.19 mm, ideally 0.25 mm+. Don't design at the limit — smaller means harder to scan;
• Output at ≥ 300 DPI: low resolution blurs and merges the narrowest bars, making the code unreadable. Vector output (PDF/SVG) is best when available;
• Quiet zone: keep blank margins at both ends — 11 modules left / 7 right for EAN-13, at least 10× the narrow element width for Code128. Quiet zones invaded by text, borders, or crop marks are the most common layout failure;
• Colors: dark bars on a light ground; black on white is safest. Avoid red bars (scanners skip red) and never invert.

Re-export a high-resolution copy from the Barcode Generator before printing, proof-test one copy, then run the batch — same rule as QR printing: never skip the live test.

Barcode vs QR Code

They don't replace each other — they address different audiences:

• Choose a barcode when the content is a short numeric ID read in bulk by scanners, cost-sensitive (plain labels), and not meant for humans — inventory, assets, ticketing, retail checkout;
• Choose a QR code when the content is a URL or structured data scanned by consumers' phones, when damage tolerance matters, or when you want a logo overlay — landing pages, payments, packaging interactivity.

Rule of thumb: machines reading IDs get barcodes; people scanning content get QR codes. Packaging often carries both — a product barcode on one side for checkout, a QR code on the back for engagement. If you go the QR route, see QR Code Not Scanning — the quiet-zone and resolution discipline carries over.

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