Key points
- Reading asks whether a code decodes; verification asks how well it is printed, measured to a standard.
- ISO/IEC 15416 grades linear barcodes, ISO/IEC 15415 grades 2D codes, and ISO/IEC 29158 grades direct part marks.
- GS1 sets minimum grades per application, such as 1.5/06/660 for retail point-of-sale barcodes.
- GS1 South Africa states that many retailers require its barcode test report when a product is listed.
- An in-line reader proves each code decodes with the right content; a formal grade needs a calibrated verifier.
Reading, verification and grading: three different questions
Reading asks whether a code can be decoded and what it says. A barcode scanner or code reader answers that on every pack. Verification, also called grading, asks how well the code is printed, measured against a standard with a dedicated, calibrated verifier. The answer is a grade, not a yes or no. GS1 UK puts the difference simply: a scanner will beep or not, whereas a verifier checks the barcode’s quality (GS1 UK).
A code can read today and still be poorly printed. It may then fail on a different scanner, at a distribution centre or at a retailer’s till. That is why retailers and GS1 care about grades, not only about whether a code scans once.
The barcode grading standards
Three ISO/IEC standards define how print quality is measured and graded. Each measures a set of parameters and takes the worst one as the grade, on a scale from 4 (A, best) to 0 (F, fail).
| Standard | Applies to | What it grades |
|---|---|---|
| ISO/IEC 15416 | Linear (1D) barcodes: EAN/UPC, ITF-14, GS1-128, Code 128 | Scan-profile grading: parameters such as symbol contrast, minimum reflectance, edge contrast, modulation, defects and decodability. |
| ISO/IEC 15415 | 2D codes: Data Matrix, QR code, GS1 DataMatrix | Image-based grading: parameters such as symbol contrast, modulation, fixed pattern damage, axial and grid non-uniformity, and unused error correction. |
| ISO/IEC 29158 | Direct part marks (DPM): dot-peen and laser-marked codes on parts | A guideline adapting 2D grading to marks on metal and plastic, with its own lighting conditions. |
What grade GS1 requires
The standards measure; the application decides what is good enough. For GS1 barcodes, the GS1 General Specifications set the minimum symbol quality. Barcodes scanned at a retail point of sale, such as EAN-13 and UPC-A, need at least 1.5/06/660, and barcodes in general distribution, including ITF-14 and GS1-128 on cases and pallets, at least 1.5/10/660. Grade 1.5 corresponds to ISO grade C (GS1 General Specifications 2026).
On logistic labels, the SSCC is the single mandatory element and is carried in a GS1-128 barcode (GS1 General Specifications 2026). GS1 also aims for retailers to be able to scan 2D barcodes at the till by the end of 2027; a GS1 DataMatrix or GS1 QR code can carry the batch or lot number and the expiry date as well as the product number (GS1 South Africa, 2D in retail).
Barcode verification for South African retailers
GS1 South Africa tests barcodes using ISO 15416 verification methods, covering size, colour, print quality and numbering, and states that many retailers require its barcode test report as a mandatory step in the product listing process (GS1 South Africa). The report tests artwork and printed samples before listing; it does not check what the production line prints every day. Codes printed on the line, especially variable data from a coder or codes printed on corrugated cases, can change with print head wear, ribbon, ink and speed.
What an in-line station can and cannot prove
An in-line reader or camera reads every code at line speed. That is the right tool for stopping packs that will not scan or carry the wrong content. It is not a substitute for grading.
| Question | In-line reader | How |
|---|---|---|
| Every code decodes at line speed | Yes | A no-read is treated as a fail and the pack is rejected. |
| The content is right for the product and batch | Yes | The decoded GTIN, batch or SSCC is compared with the expected value. |
| Print is getting worse over time | Partly | Many readers report a quality indicator per read; a falling trend is an early warning, not a grade. |
| The code meets a formal ISO/IEC grade | No | Needs a calibrated verifier under the standard’s conditions, usually offline on samples. |
| The code will scan at every retailer’s till | No | No single reader proves that; meeting the GS1 grade makes it likely. |
For a formal grade, samples are taken from production and measured on a verifier at set intervals, or whenever artwork, material or the coder changes. The in-line station then protects every pack in between. See OCR/OCV and code inspection for unit codes and carton and pallet label verification for SSCC labels.
Common causes of poor barcode grades on the line
| Cause | Effect on the code | Where to look |
|---|---|---|
| Printing too light or too dark | Symbol contrast falls; bars spread or thin. | Coder settings, ribbon or ink, and the substrate. |
| Bar width growth or loss | Bars print wider or narrower than designed. | Print gain in the artwork, print speed and pressure. |
| Quiet zone too small | Print or an edge intrudes on the clear space beside the code. | Artwork layout and label position. |
| Curved, wrinkled or shiny surface | The code distorts or reflects unevenly. | Code position, label material, reading angle. |
| Worn print head or dirty ribbon | White lines through the bars. | Print head maintenance. |