Ideal Postcodes

Postcoder is an API from Allies Computing that gives developers a single endpoint for verifying and validating customer contact data at the point of entry. Used across sectors from healthcare to retail, it's built to drop into checkout, onboarding, and account creation flows with minimal friction. What's included: Address lookup – Postcode, partial address, or coordinate-based search across Royal Mail PAF, Ordnance Survey AddressBase, and 249 countries worldwide. Bank validation – Real-time sort code and account number verification, with branch data and direct debit eligibility returned in the response. Email validation – Domain and formatting checks with disposable address detection. Mobile validation – Live network status checks across 200+ countries. OTP verification – SMS-based one-time password delivery. Clear documentation, multi-language sample code, and a straightforward REST structure mean integration is quick. 30 day free trial with no credit card required.

Postcodes.io is an open source postcode lookup API and geocoder for the United Kingdom that lets developers search, validate, and geolocate UK postcodes while retrieving detailed administrative and geographic information. The API can look up complete postcode records, reverse geocode latitude and longitude coordinates to nearby postcodes, search by partial postcode strings, find nearest postcodes to a location, and query outward codes and places. Responses can include coordinates, regions, administrative districts, counties, wards, parishes, parliamentary constituencies, statistical areas, health geographies, rural-urban classifications, and other associated codes and attributes. Bulk reverse geocoding allows large sets of coordinates to be converted into their nearest postcode areas, while autocomplete and validation methods simplify postcode entry and verification workflows.