This article explains what Swap is as a carrier in your warehouse management system (WMS) or 3PL platform — how it works, what it does behind the scenes, and what it means for your shipping labels and customs documentation.
Swap is a virtual carrier
When your WMS or 3PL calls Swap as a carrier, Swap is not physically handling your shipment. Swap acts as a virtual carrier — a middleware that sits between your system and the real shipping carrier (such as FedEx, UPS, or DHL).
This matters because it means carrier-specific requirements — supported destinations, required fields, weight formats — are determined by the end carrier, not by Swap. If you encounter a label error related to a missing field or unsupported destination, check the requirements of the carrier Swap is calling on your behalf.
How it works
When your WMS or 3PL requests a label from Swap:
Swap looks up the order in Swap Global and retrieves the corrected customs values — item values, HS codes, country of origin, and item descriptions.
Swap passes these enriched values to the actual carrier (e.g. FedEx) on your behalf.
The carrier generates the label, which is returned to your WMS or 3PL.
This ensures your commercial invoice and customs documentation reflect Swap's verified, duty-paid values — rather than the raw or inflated data from your WMS.
Note: If an order is requested through Swap but cannot be found in Swap Global, Swap will not return an error. Instead, it passes the data provided in the label request directly to the carrier and generates a label. In this case, Swap's enriched values will not be applied — only the data in the original request (e.g. from Shopify) will be used for customs.
Integration options
There are two ways to call Swap as a carrier, depending on your WMS or 3PL:
Plug-and-play integrations — some WMS and label-printing platforms already have Swap built in as a carrier option. Setup is typically a matter of adding your Swap credentials. See the full list of supported platforms: WMS and label printing technologies that integrate with Swap.
Direct API integration — if your platform doesn't have a pre-built Swap integration, you can connect directly using the Swap Shipping API. Your system calls Swap, Swap calls the carrier, and the label is returned to you. Contact your Swap account manager to get started.