Packaging and artwork checks serve as a final quality safeguard before a barcode print enters mass production. Errors after this stage—wrong digits, poor contrast, fuzzy bars, or missing quiet zones—are expensive to fix once labels, sleeves, or cartons are printed. This page highlights advice on verifying barcode artwork files before releasing them to the printer.
Validate the GTIN and check digit
Before you place any barcode graphics onto artwork, confirm the GTIN itself is valid and the check digit is correct. When you are working with multiple GTINs on multiple different products, make sure you have used the GTIN you assigned for a given product, and not a number off a different product by mistake.
The GTIN error checking algorithm uses a modulo-10 check digit calculated from the prior digits. This means a transposed digit (where two digits swap places, possible during manual data entry) could produce a valid-looking barcode that scans to the wrong product. Do not trust copy-pasted numbers from spreadsheets or emails without inspection of the result.
Try out this utility to see for yourself:
Use a dedicated check digit calculator or GTIN validator to verify every code. The GTIN validator and check digit calculator can validate GTIN-8, GTIN-12, GTIN-13, and GTIN-14 formats and flag common errors such as incorrect length or invalid check digits. See also check digit calculator for additional guidance on manual verification.
| Check | How to verify |
|---|---|
| Correct GTIN length | 8, 12, 13, or 14 digits as appropriate for the target market (North America, Canada, often expects GTIN-12) |
| Valid check digit | Recalculate using a validator |
| No leading zeros dropped | Spreadheets often strip leading zeros from GTIN-12 and GTIN-14, compare final number number from source |
| One GTIN per SKU | Each variant (size, colour, flavour) needs a distinct GTIN |
Confirm human-readable digits match encoded data
The numbers printed beneath a barcode—the human-readable interpretation (HRI)—must exactly match the data encoded in the bars. This is worth checking in case a checkout operator ever tries entering the GTIN manually following a failed scan.
Verify that:
- The HRI font is legible (typically OCR-B or a clean sans-serif at minimum 2 mm height)
- The HRI is positioned below the barcode, not above or beside it
- No digits are truncated, overlapped, or obscured by other artwork elements
- The HRI includes all digits, including the check digit
If your barcode was generated from a data file, compare the HRI against the original source. Do not rely on visual similarity—read each digit individually.
Check colour contrast and quiet zones
It is the contrast that makes barcodes work, not the specific black-and-white colors, although that pair will inherently have the most constrast. Barcodes require adequate contrast between the dark bars (typically black, dark blue, or dark green) and the light spaces (typically white, or a pale yellow/orange with sufficient reflectance). Red and gold tones often fail because many scanners use red light, making red bars appear invisible.
Contrast guidelines
| Element | Recommendation |
|---|---|
| Dark bars | Black preferred; dark blue, dark green, or dark brown acceptable if reflectance is low enough |
| Light spaces | White strongly preferred; pale yellows may work if tested, if the color suits the packaging design |
| Avoid for bars | Red, orange, gold, metallic foils (unreliable reflectance) |
| Background behind barcode | No patterns, tints, or images that interfere with quiet zones, flat white color works best |
The barcode colour legibility simulator provides a quick way to assess whether your chosen colours will scan reliably. It simulates how a scanner “sees” your colour combination and flags high-risk pairings if you are opting to use a customized barcode design on your product packaging. Choosing black bars and and white spaces is always a safe bet.
Quiet zones
Quiet zones are the mandatory blank margins on either side of the barcode. Without them, adjacent artwork or text might be interpreted as part of the barcode in the scanner’s field of view, causing misreads or no-reads.
| Barcode type | Minimum quiet zone |
|---|---|
| EAN-13 / UPC-A | 11 modules (≈ 3.63 mm at 100% magnification) on left; 7 modules on right |
| EAN-8 | 7 modules on each side |
| GS1-128 (Code 128) | 10 modules on each side |
A module is the basic unit of width in a barcode. It is equal to the width of the narrowest bar or space. All other bars, spaces and quiet zones are measured as multiples of this unit. At 100% magnification for an EAN-13 or UPC-A barcode, 1 module is approximately 0.33 mm wide.
In artwork, quiet zones must be truly empty—no crop marks, colour bleeds, or decorative elements. If your packaging design requires the barcode to sit near an edge or fold, adjust the layout or reduce barcode magnification to maintain the quiet zone.
Verify barcode dimensions and magnification
Barcodes have standard dimensions at 100% magnification. Reducing below the minimum can render bars too narrow for standard scanners to resolve.
| Barcode type | Nominal width at 100% | Typical minimum magnification | Height at 100% | Height at 80% |
|---|---|---|---|---|
| EAN-13 | 37.29 mm | 80% (≈ 29.8 mm) | 25.93 mm | ≈ 20.74 mm |
| UPC-A | 37.29 mm | 80% (≈ 29.8 mm) | 25.93 mm | ≈ 20.74 mm |
| EAN-8 | 26.73 mm | 80% (≈ 21.4 mm) | 21.31 mm | ≈ 17.05 mm |
Height can be reduced for small packaging, but excessive truncation should be avoided. Truncated bars reduce scan success at angles and through shrink wrap.
Measure the final barcode in your artwork file at print resolution, not screen resolution. A 300 dpi image viewed at 100% on a 96 dpi monitor will appear larger than it prints.
Run a physical test scan before bulk printing
Digital verification tools catch many errors, but they cannot replicate every real-world scanning condition. A physical test scan can reveal otherwise hidden issues. If you’re unable to perform such testing yourself, you may wish to consider verification testing by a barcode retailer organization.
Suggested physical test scan protocol
- Print a proof on the actual substrate and with the actual print process (offset, flexo, digital, thermal transfer). Screen proofs and laser prints are not representative of how scanner light will reflect off the product packaging.
- Allow drying time if using wet inks or adhesives. Smearing can temporarily pass and later fail.
- Scan with multiple devices: at minimum, a handheld laser scanner and a 2D imager (camera-based). If the product will sell through supermarkets, test with a multi-plane scanner if possible.
- Test at angles: not just perpendicular, but also the shallow angles typical of conveyor belts and customer self-scan.
- Test through packaging: if the barcode will be behind film, shrink wrap, or a curved surface, scan through that layer.
- Verify the decoded data: the scanner should return exactly the GTIN, with no extra digits, no missing digits, and no incorrect symbology identifier. However, do note that some scanners can be configured to drop the leading zeroes in a GTIN making a valid EAN-13 appear as a GTIN-12 when scanned.
For additional guidance on scanner types and compatibility considerations, see scanner compatibility.
Pre-flight checklist for artwork release
Use this checklist (interactive) before signing off barcode artwork for print:
- GTIN validated with independent check digit calculator
- HRI matches encoded data exactly
- Bar colour and background colour tested for contrast
- Quiet zones clear of all artwork elements
- Barcode dimensions within acceptable magnification range
- Barcode positioned away from folds, seams, and perforations
- Physical test scan passed on production-equivalent proof
- Scan data matches expected GTIN with no modifications
Common artwork errors to avoid
| Error | Why it fails | Prevention |
|---|---|---|
| Check digit wrong | Scans as wrong product or not at all | Always validate independently |
| HRI does not match bars | Retailer systems reject; potential recall | Manual digit-by-digit comparison |
| Quiet zone encroached | Adjacent artwork merges with bars | Define quiet zones as protected areas in templates |
| Bars in red or metallic | Low reflectance contrast | Use black or dark blue; test with simulator |
| Over-magnification | Exceeds packaging space; may distort | Design within 100–150% range |
| Under-magnification | Bars too narrow for reliable scanning | Never below 80% without formal deviation approval |
| Bitmap scaling distortion | Bars become uneven or blurred, scanner unable to identify where a bar ends and a space begins | Use vector based formats for your barcode files; avoid raster scaling |
References and further reading
- GS1 UK. Barcoding: Getting It Right (PDF). https://www.gs1uk.org/sites/default/files/GS1-UK-barcoding-getting-it-right.pdf
- GS1 US. Guideline: Bar Code Symbol Placement (PDF). https://documents.gs1us.org/adobe/assets/deliver/urn:aaid:aem:30071c02-969b-4b61-acc1-a44373c44ec1/Guideline-Bar-Code-Symbol-Placement.pdf
- Barcode standards and validation — overview of formal validation requirements
- GTIN validator and check digit calculator
- Barcode colour legibility simulator