Shelf Labels: The Crouch-and-Scan
Shelf-edge labels and price tickets are scanned from 40 to 80 cm — shoppers crouch, lean, and angle their phones at low shelves while holding a basket in the other hand. The viewing angle is often steep, which foreshortens the code vertically and punishes small modules. Shelf labels also live in the shadow line cast by the shelf above, in lighting that is adequate but rarely generous.
The 10:1 Rule of Thumb
At 50 cm the rule suggests 50 mm, but shelf-edge strips are rarely that tall — standard strips run 25–40 mm in height. The practical target is 30–35 mm on the flat face of the strip, compensating with a short URL and high-contrast print rather than raw size. Where the strip genuinely cannot fit 30 mm, the code belongs on the product packaging or a shelf talker instead.
Recommended Size
Print at 35 × 35 mm (about 1.4 inches) on shelf-edge strips; 25–30 mm is workable on adhesive price labels with short payloads and 300 DPI thermal-transfer printing. For bottom shelves scanned at steep crouch angles, favor the upper end — angle foreshortening effectively shrinks the code as seen by the camera.
Substrate and Printing
Shelf strips print thermal-transfer (300 DPI preferred) on plastic or coated paper strips; price guns and portable label printers vary wildly in quality. Qualify the actual printer model with real test scans — a "thermal transfer printer" category tells you nothing about the specific unit's dot control. Adhesive price labels on products face handling and refrigeration; specify stocks rated for the environment.
Placement and Practical Tips
- Keep the code on the flat front face of the strip, never wrapping over the strip's top or bottom edge where it distorts.
- Avoid the shadow line cast by the shelf above; codes sitting in shadow lose the contrast margin that makes scanning forgiving.
- If prices change often, link the code to the product page via a stable SKU-based URL, so the label never needs reprinting for a price change.
- On deep shelves, keep the code toward the front edge — codes half-hidden behind the product in front simply don't get scanned.
- For refrigerated cases, condensation is a factor; specify moisture-resistant label stocks.
Common Mistakes
- 203 DPI price-gun printing of a dense code — modules merge and the code dies at birth.
- Encoding the price instead of the SKU, guaranteeing a full reprint with every price change.
- Codes on the bottom shelf placed for a standing adult's eye line rather than a crouching shopper's.
- Assuming the strip printer in the back office matches the one at the pilot store — qualify every model.