GeoJSON and KML are the two most widely used open formats for encoding geographic data, yet they serve different audiences and ecosystems. GeoJSON is a lightweight, JSON-based specification defined by RFC 7946. It represents geometry types such as Point, LineString, Polygon, and their multi-variants alongside arbitrary properties. Because it is valid JSON, it integrates naturally with JavaScript, REST APIs, and modern web mapping libraries like Leaflet, Mapbox GL JS, and OpenLayers.
What is GeoJSON?
GeoJSON is an open standard format for representing simple geographic features along with their non-spatial attributes. Based on JSON (JavaScript Object Notation), it is human-readable, easy to parse in virtually every programming language, and natively supported by web browsers. The specification, formalized as RFC 7946, defines how to encode points, lines, polygons, and collections of these geometries alongside custom property data.
What is KML?
KML, or Keyhole Markup Language, is an XML-based format originally developed for Google Earth. It excels at rich cartographic styling — you can embed icons, colors, line widths, and even 3D perspectives directly in the file. KML also supports time-based animations, network links for streaming data, and ground overlays, making it the go-to choice for presentations, virtual tours, and applications that require visual fidelity out of the box.
Key Differences at a Glance
| Feature | GeoJSON | KML |
|---|---|---|
| Base format | JSON | XML |
| File size | Compact | Larger (XML overhead) |
| Styling | Not included | Built-in (icons, colors, line widths) |
| 3D support | Limited (altitude) | Full (camera, tilt, roll) |
| Web library support | Universal | Moderate |
| Default CRS | WGS 84 (EPSG:4326) | WGS 84 (EPSG:4326) |
| Specification body | IETF (RFC 7946) | OGC |
When to Use GeoJSON
If you are building a web application, consuming data from an API, or performing server-side geoprocessing, GeoJSON is almost always the better fit due to its compact size, simple parsing, and universal library support. Libraries like Leaflet, Mapbox GL JS, and OpenLayers consume GeoJSON directly without conversion.
When to Use KML
If your primary output is Google Earth, Google Maps, or you need to share styled maps with non-technical stakeholders, KML provides a richer visual experience without additional rendering code. KML also supports network links and overlays for streaming live data.
Converting Between GeoJSON and KML
In practice, many GIS professionals need both formats at different stages of a project. Tools like GeoDataTools let you import either format, visualize it on an interactive map, apply filters, and export to the other format in seconds — eliminating the need for desktop GIS software or command-line conversion scripts.
FAQ
Can GeoJSON store styling information?
No, GeoJSON does not include a styling specification. Styling is applied at the rendering layer by the mapping library you use, such as Leaflet or OpenLayers. A proposal called "simplestyle" exists but is not part of the official spec.
Which format is better for large datasets?
GeoJSON is generally more compact due to JSON's lighter syntax compared to XML. For very large datasets, consider formats like GeoPackage or FlatGeobuf which are optimized for size and streaming.
Do both formats support 3D coordinates?
Both support altitude as a third coordinate value. However, KML provides far richer 3D capabilities including camera angles, tilts, and fly-to animations that GeoJSON does not support.