What Is .kml

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Last updated: April 10, 2026

Quick Answer: KML (Keyhole Markup Language) is an XML-based file format for representing geographic data, including coordinates, maps, and location markers. Originally developed by Keyhole Inc. and acquired by Google in 2004, it became an open international standard (OGC KML 2.2) in 2008 and is now the standard format for sharing geographic information across mapping applications like Google Earth and Google Maps.

Key Facts

KML was created by Keyhole Inc. in 2001 and acquired by Google in 2004, becoming the foundation for Google Earth's mapping technology
The format became an international standard (OGC KML 2.2) on May 14, 2008, established by the Open Geospatial Consortium
A single KML file can contain up to 65,536 placemarks with coordinates, though performance depends on the application and device capabilities
KML supports 3D visualization including altitude data, camera angles, and 3D model overlays through collada (.dae) file integration
File size typically ranges from a few kilobytes for simple point data to several megabytes for complex geographic datasets with imagery and 3D models

Overview

KML (Keyhole Markup Language) is a file format used to display geographic data in internet-based mapping applications. It is structured as an XML document that encodes geographic information such as points, lines, polygons, images, and 3D models, making it the standard way to share location-based information across different platforms.

The format originated with Keyhole Inc.'s mapping software in 2001 and gained widespread adoption after Google acquired the company in 2004. Google integrated KML into Google Earth and Google Maps, eventually leading the Open Geospatial Consortium (OGC) to formally standardize it as KML 2.2 on May 14, 2008. Today, KML is the de facto standard for geographic data interchange and is supported by countless mapping, GIS, and navigation applications worldwide.

How It Works

KML files operate using a hierarchical XML structure that defines geographic features and their properties. Here's how the format functions:

Coordinate System: KML uses latitude and longitude coordinates in the WGS84 datum, the same standard used by GPS systems worldwide, allowing precise location mapping across any geographic region.
Placemarks: Individual locations are represented as placemarks, which can contain a name, description, geometry (point, line, or polygon), and styling information including color, icon, and label properties.
Hierarchy and Organization: KML supports nested folder structures that organize multiple features into logical groups, making it easy to manage large datasets with hundreds or thousands of geographic elements.
Styling and Appearance: The format includes style definitions that control how features appear on a map, including line colors, widths, fill patterns, and custom icons for different feature types.
Time-Based Data: KML supports temporal information through TimeSpan and TimeStamp elements, enabling animations that show how geographic features change over time intervals.

Key Comparisons

KML shares space with other geographic data formats, each with distinct strengths:

Format	Structure	Best For	File Size
KML	XML-based, human-readable	Web mapping, Google Earth, general GIS sharing	Medium (readable compression)
GeoJSON	JSON-based, lightweight	Web applications, REST APIs, modern development	Smaller files, faster parsing
Shapefile	Binary format, multiple files	Professional GIS, desktop applications like ArcGIS	Compact binary, requires multi-file bundle
GPX	XML-based, track-focused	GPS tracking, fitness data, hiking routes	Small, optimized for point sequences

While GeoJSON has gained popularity for web development due to its lightweight JSON structure, KML remains the preferred format for Google Maps integration and provides superior support for visual styling, 3D models, and time-based animations. Shapefiles dominate professional GIS workflows but require multiple companion files, whereas KML is a single, self-contained file.

Why It Matters

Universal Compatibility: KML's status as an international standard ensures that geographic data created in one application can be seamlessly imported into dozens of others, from Google Earth to ArcGIS to open-source mapping tools.
Accessibility: The human-readable XML format allows users to manually edit KML files with any text editor, making it accessible to non-programmers while remaining powerful enough for complex geographic projects.
Web Integration: KML's tight integration with Google Maps and Google Earth gives it unmatched reach for sharing location data online, enabling real estate listings, tourism information, disaster response mapping, and countless other applications.
3D and Temporal Capabilities: Unlike simpler formats, KML's support for altitude data, 3D models, camera perspectives, and time-based animation opens possibilities for immersive geographic visualization and historical or predictive modeling.

KML's enduring relevance stems from its balance of simplicity and power. Whether you're a casual user sharing a hiking route on Google Earth or a GIS professional managing complex geographic datasets, KML provides a reliable, standardized format that bridges the gap between professional geospatial tools and everyday mapping applications. Its continued adoption across industries—from urban planning and environmental monitoring to real estate and emergency management—demonstrates that despite newer alternatives, KML remains the most practical choice for most geographic data sharing needs.