A look at the creative things developers are building with our sister API
Every so often, we discover projects built with Postcodes.io and it makes our day. Seeing how developers, researchers, and hobbyists put postcode data to work is something we genuinely love about the Postcodes.io community.
What surprised us most when pulling this list together was the range. We expected to find address forms or delivery tools, but what we found instead was creative projects that span aircraft radar, logistics, charity fieldwork, academic research, and civic data infrastructure. The breadth is wider than we anticipated, and we think it is worth celebrating.
Below are ten projects from the Postcodes.io community that caught our attention. Some are polished tools used by thousands of people, while others are personal projects. All of them show what becomes possible with postcode data.
Postcodes.io is our open-source UK postcode lookup and geocoding API, maintained by Ideal Postcodes and updated regularly with data from the ONS Postcode Directory, Ordnance Survey Open Names, and the Scottish Postcode Directory. Enter a postcode and the API returns a detailed set of geographic and administrative data, including latitude, longitude, parliamentary constituency, local authority, NHS region, and the Index of Multiple Deprivation.
Brian Willows at Graith Internet built a desktop widget called RadarScope: a circular, phosphor-green radar display that floats in the corner of your screen and plots live aircraft flying overhead using real ADS-B transponder data. It is beautiful, useful, and magical to watch.
Postcodes.io plays a simple but important role. You enter your UK postcode once, and RadarScope resolves your latitude and longitude. From that point on, the radar is centred on your home, and every aircraft blip is calculated relative to that position, including distance, bearing, altitude, and track, all from a single postcode lookup at setup.
What makes the project particularly interesting is how Brian approached the build. Rather than working conversationally with an AI coding tool, he wrote a complete specification document first, covering the geometry, data sources, threading model, and cross-platform requirements, then handed the spec to Claude Code to implement.
Read Brian's full write-up here.
Since June 2024, every major fuel retailer in the UK has been legally required to report their pump prices to the government in near-real time through an API run by the Competition and Markets Authority, and almost nobody was building with it.
Wayne Austin decided to change that. He built PetrolFinder.uk, a tool that pulls live prices from more than 7,500 stations and lets drivers find the cheapest fuel near them. The architecture syncs the government data every five minutes into a PostGIS database, so searches are fast and never touch the upstream API directly.
Postcodes.io handles the geocoding layer. When a user searches by postcode, PetrolFinder converts it to a latitude and longitude, then runs a geospatial query to find nearby stations ranked by price.
Election Maps, built and maintained at principalfish.co.uk, is an interactive map of UK parliamentary results and seat predictions covering Westminster, Holyrood, and other parliaments. It has been running through multiple election cycles and is updated as new polling data and boundary changes arrive.
Postcodes.io powers the postcode search feature. A visitor can type in their postcode and the map jumps to their constituency, showing results or predictions for their seat. It is a small feature in a larger application, but it is the one that makes the map feel personal rather than abstract.
Alexei Schwab, a GIS and information manager at the British Red Cross, built a simple UK postcode geocoding tool in April 2024. The prompt was a conversation with a colleague who was using an Excel plugin to map addresses, a tool that worked but came cluttered with advertisements and unnecessary overhead.
Alexei built a clean replacement using Python and Streamlit, hosted on Streamlit.io, that lets Red Cross staff geocode postcodes quickly for field mapping. Postcodes.io handles the geocoding, and the tool outputs coordinates that feed directly into mapping workflows.
This project is a good example of how access to reliable postcode data can improve the day-to-day work of people who are not developers by trade.
Not every project built on Postcodes.io produces a web app or a desktop widget. Some of the most valuable work happens in research contexts, where the need is to join postcode-level data to wider administrative geographies for analysis.
PostcodesioR, built by Eryk Walczak and maintained under rOpenSci, is an R package that wraps the Postcodes.io API for data scientists and social scientists working with UK geocoded data. A common task in this kind of work is aggregating postcode-level records up to counties, regions, constituencies, or NHS areas, the kind of geographic joining that postcodes make possible but that requires a reliable data source underneath.
The package was formally peer-reviewed and published in the Journal of Open Source Software in 2023. It is also available on CRAN.
Intelligent document processing is the discipline of extracting structured information from unstructured text, scanned forms, and Optical Character Recognition (OCR) output. It is also, it turns out, a genuinely useful place for postcode data.
A developer going by angangwa on GitHub built a Python library specifically for parsing UK postcodes out of unstructured text, with a focus on document processing use cases. The library is directly inspired by Postcodes.io's methodology and uses the ONS Postcode Directory data in the same way.
If you are processing thousands of scanned forms or documents that mention addresses, you need a reliable way to identify and extract postcodes from imperfect text, then validate and geocode them. This library handles the extraction and validation layer of that pipeline.
The 2024 UK general election brought significantly redrawn constituency boundaries. Many postcodes that had belonged to one constituency for years suddenly straddled two new ones, and the standard centroid-based lookup methods gave incorrect results for people living near the edges.
A developer called asibs on GitHub built an open-source tool to solve this properly. The project generates an accurate postcode-to-constituency lookup that accounts for postcodes overlapping multiple boundaries, rather than simply assigning each postcode to whichever constituency its centroid falls within. The output can be downloaded as a CSV or a SQLite database, and the code is designed so that anyone running a constituency-finder on their website can use it directly.
Steven Curtis published a tutorial on Medium using the Postcodes.io autocomplete endpoint to build a postcode search experience in Swift for iOS. As a user types, the app queries the API for matching postcodes and presents a live list of suggestions, which the user can then select to trigger a full lookup.
The project demonstrates how to use UISearchBarDelegate in a real-world context and is a good reference for any iOS developer looking to add postcode search to an app.
Conor Graham built his first-ever Python application, using Postcodes.io as the data source. The project queries three endpoints, postcode lookup, validation, and nearest postcodes, and presents the results through a simple terminal interface.
The Index of Multiple Deprivation is the official government measure of relative deprivation for small areas in England, ranking every lower-layer super output area from most to least deprived across seven domains including income, health, education, and crime. It is a dataset that researchers, councils, charities, and policy teams use regularly.
The IMD Postcode Checker, originally built by Charles Roper and maintained by the Field Studies Council, is a simple PHP and SQLite tool that lets users look up the deprivation rank for a UK postcode. It normalises and validates postcodes using Postcodes.io-style methodology before querying the deprivation data.
We would love to hear about it. If you have used the API in a project, however large or small, feel free to reach out or share it with us.