Postcodes.io API

Overview

Measurement Record

What actually happened when we called this API from our own infrastructure. Every value below was recorded by the request, not copied from the provider's documentation.

Request

GET https://api.postcodes.io/postcodes/SW1A1AA

Result

HTTP 200 · application/json · 1,943 bytes · compressed

Response time

37 ms (median of 3) · fastest 27 ms

Transport

TLSv1.3 · TLS_AES_256_GCM_SHA384 · certificate issued by Google Trust Services

Browser CORS

Allowed — Access-Control-Allow-Origin: *

Served by

cloudflare

Recorded

2026-08-10

Fields Returned

Top-level fields present in the response we captured, with the type and value we actually received.

Captured Response

Captured from a real request to https://api.postcodes.io/postcodes/SW1A1AA on 2026-08-10. Long arrays and nested objects are truncated to keep the shape readable.

{
  "status": 200,
  "result": {
    "postcode": "SW1A 1AA",
    "quality": 1,
    "eastings": 529090,
    "northings": 179645,
    "country": "England",
    "nhs_ha": "London",
    "longitude": -0.141563,
    "latitude": 51.50101,
    "european_electoral_region": "London",
    "primary_care_trust": "Westminster",
    "region": "London",
    "lsoa": "Westminster 018C",
    "msoa": "Westminster 018",
    "incode": "1AA",
    "…": "(32 more fields)"
  }
}

Implementation Example

Calls a real endpoint of this API. Replace any placeholder credentials with your own key.

const url = "https://api.postcodes.io/postcodes/SW1A1AA";
const response = await fetch(url);
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

import requests

url = "https://api.postcodes.io/postcodes/SW1A1AA"
headers = {}

response = requests.get(url, headers=headers, timeout=30)
response.raise_for_status()
data = response.json()
print(data)

curl "https://api.postcodes.io/postcodes/SW1A1AA"

What Can You Build?

// Geocode an address to latitude/longitude
const address = '1600 Amphitheatre Parkway, Mountain View, CA';
const response = await fetch(`https://postcodes.io`);
const data = await response.json();
const location = data.results?.[0] || data;
console.log('Latitude:', location.lat || location.latitude);
console.log('Longitude:', location.lon || location.longitude);

// Get location from IP address
const response = await fetch(`https://postcodes.io`);
const data = await response.json();
console.log('Country:', data.country || data.country_name);
console.log('City:', data.city);
console.log('Coordinates:', data.lat || data.latitude, data.lon || data.longitude);

// Get coordinates and calculate distance
const response = await fetch(`https://postcodes.io`);
const data = await response.json();
const loc = data.results?.[0] || data;
const lat1 = loc.lat || loc.latitude || 0;
const lon1 = loc.lon || loc.longitude || 0;
// Haversine distance formula
const R = 6371;
console.log(`Location: ${lat1}, ${lon1}`);

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

How This API Fails

We deliberately sent this API a broken request and recorded exactly what came back on 2026-08-10. Knowing the shape of an error before you hit it makes error handling much easier to write.

{
  "status": 404,
  "error": "Resource not found"
}

Common Errors & Troubleshooting

Generated guidance based on this API's documentation, not observed by us. Treat it as a starting point and check against the provider's own error reference.