Pick-to-Light & Put-to-Light

Pick-to-Light and Put-to-Light are visual guidance technologies that use rows of illuminated indicators and digital displays mounted on shelving to tell warehouse operators exactly where to pick from or place items, cutting search time and virtually eliminating pick errors in high-volume, fast-moving operations.

Each storage location — a shelf slot, a flow-rack lane, a bin — has a small light module with a numeric display and a confirmation button. When an order is released to a zone, the WMS sends pick instructions to the light controller network, and the lights illuminate at every location containing an item for that order, showing the quantity to pick on the digital display. The operator simply walks the line, picks from every lit location, and presses the button to confirm, which extinguishes the light and reports the pick back to the WMS in real time.

Because there is no handheld scanner, no screen to read, and no paper pick list, cycle times per pick can drop to 4-6 seconds in well-tuned lines, and pick accuracy commonly reaches 99.9% or higher since the light itself acts as a physical check against picking from the wrong slot.

Put-to-Light reverses the flow: instead of guiding a pick from a single order, it guides the distribution of a batch-picked tote into multiple order totes or cartons arranged along a sorting wall. A worker picks a large batch of one SKU, scans it once, and the lights illuminate on every downstream slot that needs that item along with the quantity — commonly used for e-commerce wave picking, kitting, and store-replenishment breakdown. This decouples picking from sortation, letting each stage run at its own optimal pace.

• Batch pick once upstream, distribute to many orders downstream without re-scanning per order
• Ideal for high-SKU-velocity, low-line-count orders (e-commerce, retail replenishment)
• Reduces travel distance because pickers stay in one aisle instead of walking the whole warehouse per order

Light-directed picking pays off most in zones with high order density and stable, well-known SKU locations — think fast-moving consumer goods, pharmacy distribution, or e-commerce fulfillment of small parts. It is less suited to slow-moving, high-SKU-variety storage where the fixed cost of wiring a light module to every slot cannot be justified by throughput. Many operations combine it with voice picking or RF scanning: light-directed for the A-movers in flow racks, and mobile-device picking for reserve or bulk storage.

• Best fit: high-velocity pick faces, flow racks, pick-and-pass zones
• Weak fit: pallet storage, low-turnover SKUs, seasonal or highly variable assortments

Pick-to-Light hardware is typically driven by a dedicated light controller (PLC-style) that receives pick lists from the WMS over a serial, Ethernet, or middleware interface, translating order lines into physical slot addresses. The WMS remains the system of record for inventory and order status — the light controller is a real-time execution layer sitting between the WMS and the shelf. Getting the slot-to-address mapping right during setup, and keeping it synchronized whenever a slot's SKU assignment changes, is the single most common implementation pitfall, since a stale mapping causes the wrong light to fire and defeats the whole point of the system.

• Slot-to-light address mapping must stay in sync with slotting changes in the WMS
• Real-time confirmation feedback closes the loop so the WMS always reflects true pick status
• Works alongside barcode verification for extra accuracy on high-value or regulated items