What Is Put-to-Light? How It Works And When To Use It

A sorting technology that uses lights to guide workers when placing picked items into order containers.

Put-to-Light A sorting technology that uses lights to guide workers when placing picked items into order containers. This method replaces paper sort sheets or spoken instructions with illuminated indicators that show where each picked item should go, speeding up sorting and reducing errors.

Put-to-light systems are best known for their simplicity: the picker scans a tote or SKU, lights on a modular rack or shelving unit indicate the correct order destinations, and the operator places the item where the light directs. The system can confirm placement by counting button presses, barcode scans, or weight confirmation. That minimal interaction produces measurable increases in throughput for multi-item orders and kit assembly.

How Put-to-Light Works

At its core, a put-to-light installation consists of three elements: light modules mounted near order bins, a controller or local PLC, and host software (often integrated with WMS) that sends instructions. When a picker scans an item or tote, the system identifies which orders need that SKU and sends signals to light the corresponding destinations. Lights typically flash with a quantity indicator (a number display) and may include push-buttons for confirmation.

Confirmation methods vary. The most common are:

• Light And Button: The light illuminates and the operator presses the adjacent button to confirm the put; the system increments the count.
• Scan-To-Confirm: The picker scans the order bin barcode when placing the item, providing an auditable confirmation.
• Weight Or Sensor Confirmation: Weight sensors or optical sensors confirm the item presence when higher assurance is required.

Why Warehouses Use Put-to-Light

Put-to-light reduces cognitive load on pickers by removing the need to read pick lists or memorize destinations. That translates into faster sort cycles, lower error rates, and easier training for temporary staff—critical advantages during seasonal peaks or high-SKU e-commerce fulfillment.

Operational benefits include:

• Speed: Light guidance shortens decision time at each placement, increasing orders processed per hour.
• Accuracy: Visual confirmation and one-touch acknowledgement reduce mis-sorts compared with manual methods.
• Flexibility: Modular lights can be reconfigured for different order profiles or seasonal products.

Typical Use Cases

Put-to-light excels where many small, multi-line orders are assembled from a common pick face—examples include apparel, consumer electronics, subscription boxes, and kitting operations. It’s also effective in returns processing where items must be routed into disposition bins quickly.

Less suitable applications are bulk pallet picking or very large single-line orders where conveyor sortation or pallet sort systems are a better fit.

How It Integrates With Warehouse Systems

Put-to-light is often integrated with a Warehouse Management System (WMS) or an order management platform. The host system determines which orders require a SKU and sends real-time instructions to the put-to-light controller. Integration points typically include order release, shelf/bin mapping, inventory deduction, and confirmation events for audit trails.

Integration patterns range from simple API calls to full bi-directional messaging. For high-volume operations, tight WMS integration enables dynamic slotting and real-time reallocation of destinations to keep throughput balanced.

Metrics To Monitor

Track these KPIs to evaluate put-to-light performance:

• Orders Per Hour: Measures throughput improvement against baseline manual sorting.
• Error Rate: Mis-picks per thousand lines processed; put-to-light should reduce this.
• Touch Time: Seconds per put action; includes travel and placement.
• Utilization: Percentage of time operators spend on productive puts versus idle or wandering.

Practical Example

A mid-sized apparel fulfillment center replaced a paper sort rack with a 48-destination put-to-light array for wave picking evening shifts. Operators who previously processed 45 orders/hour increased to 70 orders/hour post-deployment while errors dropped by 60%. Training time for seasonal hires decreased from three days to two half-day sessions.

Common Pitfalls And Tips

Successful deployments require careful slot mapping and network planning. Avoid these common mistakes:

• Poor Slot Layout: Packing dissimilar SKUs into adjacent destinations creates confusion; group by velocity and size.
• Insufficient Integration: Using put-to-light as an island system without WMS confirmation can create reconciliation work.
• Power And Wiring Overlooked: Underestimating power drops, cable runs, and conduit can delay installation.

Helpful tips include starting with a pilot lane, using clear numeric displays on modules, and pairing put-to-light for final sort with zone picking at the pick-face.

In short, the Put-to-Light A sorting technology that uses lights to guide workers when placing picked items into order containers. When applied to the right workflows it raises throughput, lowers errors, and simplifies seasonal staffing, provided you plan slot layout, integration, and confirmation methods carefully.