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Where to find it: Settings → Developers → API Documentation — Open in OTO ↗
Most checkouts guess at shipping. A flat rate, a table of postcodes, a promise of “3–5 working days” that nobody has checked against a carrier since it was written.

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What the API is for

OTO already knows, for a given origin, destination and parcel, which carriers will take it, what each will charge you, and how long each usually takes. The checkout API exposes that to your storefront at the moment it matters — while the customer is deciding. This is the same engine that carrier selection uses internally. The difference is only who is asking.

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Requesting options

POST /rest/v2/checkOTODeliveryFee

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What comes back

A list of delivery options, one per carrier service that will accept the shipment.

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Estimated delivery and pickup times

The two time fields answer different questions, and both belong on a checkout. Average delivery time is the duration: how long this service usually takes on this lane. Pickup cut-off time is the deadline: order after it and the clock starts tomorrow.
The cut-off is what makes a delivery promise honest“Next-day delivery” shown at 9pm is a promise the business cannot keep, and the customer finds out a day later. “Order within 4 hours for delivery tomorrow” is the same information, told in time to act on.Cut-off times are also the most effective urgency you can put on a checkout, precisely because they are true. The countdown is a fact about your operation, not a marketing device.

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Putting it on a checkout

  1. The customer enters a delivery address.
  2. Your storefront calls checkOTODeliveryFee with that city, the cart’s weight, and the hub you would ship from.
  3. You present the options you want to offer — usually cheapest and fastest rather than all of them — with the estimate and, where it is close, the cut-off.
  4. The customer’s choice becomes the delivery option on the order, so fulfillment ships what was actually sold.
Show fewer options than you receiveA response with nine carriers is a list to choose from, not a menu to display. Checkouts convert worse when shipping becomes a decision with nine branches.Two or three named by outcome — Standard, arrives Tuesday and Express, arrives tomorrow — use the same data and ask less of the customer.