We’ve all been there at some point. A client sends over a spreadsheet full of addresses and asks you to plot them on a map. It's a familiar request in GIS, and unless you're lucky enough to be given coordinates, you'll need to run a geocoding process to get the data ready.
Geocoding is the process of converting a written location — such as a postcode, address, or place name — into geographic coordinates that can be used in a mapping or spatial analysis tool. It’s a key part of many GIS workflows, and there are lots of tools available to help with it, both free and paid. Each comes with its own strengths and limitations, depending on what you're working on.
Here are a few tools I regularly use and would happily recommend.
Paid options
Google Maps Geocoding API
Google’s Geocoding API is one of the most widely used services out there. It’s fast, accurate, and particularly strong in urban areas and countries with well-developed address systems. It supports both forward and reverse geocoding, along with localisation and component filtering. However, you’ll need to pay per request, and secure an API key before use. There’s no built-in batch geocoding, but it can be handled through scripting if needed. If you're already using Google Maps elsewhere in your project, this service is easy to slot in.
ArcGIS World Geocoding Service
If you're working in the Esri ecosystem, the ArcGIS World Geocoding Service is a solid choice. It integrates with ArcGIS Pro, ArcGIS Online, and the wider suite of Esri tools. It supports both single lookups and batch geocoding, and the quality of its results is excellent, especially in sectors like planning, infrastructure, and asset management. It does come with a cost, calculated in credits, but for many organisations already using ArcGIS, it fits right into existing workflows.
Free tools
Nominatim (OpenStreetMap)
Nominatim is a free and open-source geocoder built on OpenStreetMap data. It's a great tool for quick geocoding tasks or lightweight integration into custom projects. It supports global coverage and has a reasonably good level of detail, especially in well-mapped areas. The interface is straightforward, and you can run batch jobs using external tools. There are usage limits if you’re relying on the public API, but it’s possible to host your own instance if you need more control. The recent release of Nominatim 5.0 brought some solid performance and codebase improvements, making it even more appealing for developers.
Mapbox Geocoding API
Mapbox offers a slick and developer-friendly geocoding service, built using a combination of OpenStreetMap and other open data. It supports both forward and reverse geocoding and is well-suited to web and app development. While it's technically a paid service, the free tier is generous (up to 100,000 requests a month at time of writing), making it accessible for smaller projects. Mapbox also offers excellent documentation and stylish base maps, which makes it a good choice for frontend-heavy work.
And what if there's no address? Sometimes you're dealing with places that don't have formal addresses at all — rural sites, construction areas, nature reserves. These kinds of locations are tricky for traditional geocoding tools.
What3Words
What3Words takes a different approach. It divides the world into a grid of 3-metre squares, each assigned a unique three-word combination. It’s particularly useful in areas without street addressing, or when you need a simple way to describe a precise location. The API is free for low volumes, easy to use, and works well alongside more traditional methods. It’s become quite popular in logistics and emergency services for good reason.
Each tool has its place depending on your use case. For simple tasks, Nominatim or Mapbox might be all you need. For more complex or high-volume work, Google or ArcGIS offer enterprise-grade solutions. And for edge cases, like unnamed locations or remote sites, What3Words can be a real lifesaver.
Whichever tool you choose, having a few go-to geocoding options in your kit makes life in GIS a lot easier.
At Rose Tinsley Consulting, geocoding is just one of the many tools we use to help clients unlock the power of place. By staying flexible and drawing on a range of geocoding services, we’re able to tailor our approach to fit each project’s needs. It’s part of our broader commitment to making geospatial data accessible, meaningful, and impactful for the clients we serve.
