Validate delivery postcodes in WooCommerce checkout

The problem

WooCommerce's built-in shipping zones rely on manually maintained postcode lists that go stale. When you start delivering to a new area, or stop delivering to one, updating those lists requires developer time. And when an order slips through to an area you don't cover, the refund and support cost is yours.

How Delivery Zone solves it

Wire the Delivery Zone API into WooCommerce shipping rate calculation. Your zones are managed in one dashboard, the API returns the correct price or rejection reason, and WooCommerce shows the result at checkout — all without manually editing postcode lists.

Example API request

# Server-side: check whether a postcode can be delivered to
curl -X POST https://api.deliveryzone.fi/v1/check \
  -H "X-Api-Key: dz_live_..." \
  -H "Content-Type: application/json" \
  -d '{"destinationPostcode":"00100","basketValueCents":4500}'

# response
{
  "canDeliver": true,
  "zone": "Helsinki Center",
  "priceCents": 590,
  "reason": null
}

// Server-side only — never expose your API key in browser code
const res = await fetch('https://api.deliveryzone.fi/v1/check', {
  method: 'POST',
  headers: {
    'X-Api-Key': process.env.DZ_KEY,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({ destinationPostcode: postcode, basketValueCents: basket }),
});
const data = await res.json();
if (!data.canDeliver) {
  showError(data.reason); // e.g. "OUT_OF_ZONE"
} else {
  setShippingFee(data.priceCents);
}

// PHP — server-side, keep API key out of frontend
$r = wp_remote_post('https://api.deliveryzone.fi/v1/check', [
  'headers' => [
    'X-Api-Key'    => get_option('dz_api_key'),
    'Content-Type' => 'application/json',
  ],
  'body' => json_encode([
    'destinationPostcode' => $postcode,
    'basketValueCents'    => $basketCents,
  ]),
]);
$data = json_decode(wp_remote_retrieve_body($r), true);
if (!$data['canDeliver']) return [];
foreach ($rates as $rate) {
  $rate->cost = $data['priceCents'] / 100;
}

Example customer-facing message

We don’t deliver to this postcode. Please check the postcode or choose a different delivery address. Your order has not been charged.

Who this is for

WooCommerce store owners

WooCommerce developers

WordPress agencies building delivery shops

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WooCommerce integration guide PHP integration Checkout validation use case