UK address validation API guide — from key to production

How do I authenticate with the API?

Pass your API key as a Bearer token on every request, and keep it server-side:

const headers = {
  Authorization: "Bearer " + process.env.AUTOPOSTCODE_KEY,
};

How do I look up addresses for a postcode?

A lookup returns all PAF addresses for a postcode so the user can pick the exact one:

const res = await fetch(
  "https://api.autopostcode.com/v1/lookup?postcode=SW1A1AA",
  { headers }
);
const { addresses } = await res.json();
// [{ line1, town, postcode, uprn }, ...]

How do I validate a full address?

Validation confirms a supplied address is real and deliverable, and returns the clean form:

const res = await fetch("https://api.autopostcode.com/v1/validate", {
  method: "POST",
  headers: { ...headers, "Content-Type": "application/json" },
  body: JSON.stringify({ line1: "10 Downing St", postcode: "SW1A 2AA" }),
});
const { valid, formatted, uprn } = await res.json();

How should I handle errors?

Branch on the HTTP status so failures are graceful and rate limits are respected:

What are the integration best practices?

• Keep the API key server-side, never in the browser
• Cache stable postcode lookups to cut repeat calls
• Store the UPRN as a permanent address identifier
• Soft-warn on failed validation instead of hard-blocking

See the endpoint-level UK address validation API overview, start fast with the API quickstart, and read every parameter in the REST API reference.

A modern, UK-first alternative

AutoPostcode uses the same Royal Mail PAF data as Loqate, Fetchify and Ideal Postcodes, with a clean REST API and an affordable per-lookup price — get your API key and integrate today.