KML (Keyhole Markup Language) files are used by Google Earth, GPS devices, and mapping applications to store geographic data — points, lines, polygons, and their associated attributes. If someone sends you a .kml or .kmz file and you need to see what's inside, you don't need to install Google Earth or any desktop GIS software. You can view KML files online for free, directly in your browser, using GeoDataTools.

What is a KML File?

KML stands for Keyhole Markup Language. It is an XML-based format originally developed by Keyhole Inc. and later acquired by Google. The format became an international standard under the Open Geospatial Consortium (OGC). KML files describe geographic features — including their geometry, styling, and extended attribute data — in a human-readable XML structure.

Common uses of KML files include:

Exporting routes, waypoints, and tracks from GPS devices
Sharing location data from Google My Maps and Google Earth
Distributing geographic datasets from government agencies and research institutions
Storing flight paths, shipping routes, and field survey data

A .kmz file is simply a zipped version of a KML file (and sometimes accompanying image assets). Both formats contain the same geographic information and can be opened with the same tools.

How to View a KML File Online with GeoDataTools

GeoDataTools is a free, browser-based KML file viewer. No account, no installation, and no server upload required — your file is processed entirely inside your browser. Here is how to open and explore a KML file in a few steps:

Step 1 — Open the app. Navigate to GeoDataTools in any modern browser (Chrome, Firefox, Edge, or Safari).
Step 2 — Load your KML or KMZ file. Drag and drop your .kml or .kmz file onto the map area, or click the upload button to browse your local files. Both formats are supported natively — you do not need to unzip a KMZ file first.
Step 3 — Explore features on the interactive map. Your KML data appears instantly on an interactive slippy map. Points, lines, and polygons are rendered with their geometry. Pan and zoom freely to inspect any area of interest.
Step 4 — Click features to inspect properties. Click on any feature on the map to open a popup showing all associated attribute data from the KML's ExtendedData or description fields — names, descriptions, custom fields, and more.
Step 5 — Filter and export. Use the filter panel to narrow down features by geometry type or attribute values. When ready, export the data as GeoJSON, CSV, or back to KML for use in other applications.

The entire process takes under a minute, and because nothing leaves your device, it is safe to use with sensitive or proprietary geographic data.

What You Can Do with Your KML File

Viewing the geometry on a map is just the starting point. Once your KML file is loaded in GeoDataTools, you have a full set of tools at your disposal:

Visualize on an interactive map. All features render on a zoomable, pannable base map. Switch between satellite, street, and terrain backgrounds to get the context you need.
Inspect the attribute table. Open the attribute table to view all feature properties in a sortable, searchable grid — useful for datasets with dozens of attributes per feature.
Filter features. Apply filters based on geometry type (show only polygons, for example) or attribute values (show only features where status = 'active'). This is especially useful for large KML files with hundreds or thousands of features.
Convert KML to GeoJSON. GeoJSON is the standard format for web mapping. Use the built-in KML to GeoJSON converter to transform your data into a format ready for Leaflet, Mapbox GL JS, Turf.js, or any GeoJSON-aware API — all without leaving the browser.
Export filtered subsets. Apply a filter first, then export — you get a clean output file containing only the features that match your criteria, saving post-processing time.

KML vs KMZ: What's the Difference?

The difference between KML and KMZ is straightforward:

KML is an uncompressed XML text file. It is human-readable and can be opened in any text editor. File sizes can be large for complex datasets.
KMZ is a ZIP archive containing one or more KML files, plus optional resources such as custom icon images and overlay graphics. It is the preferred distribution format because it is significantly smaller due to compression.

From a data perspective, they are equivalent. GeoDataTools handles both formats transparently — drop in a .kmz and it extracts and reads the embedded KML automatically.

Why Use an Online KML Viewer Instead of Google Earth?

Google Earth is the most well-known KML viewer, but it is not always the right tool for the job. Here are the practical reasons to use a browser-based KML viewer like GeoDataTools instead:

No installation required. Google Earth Pro is a 100 MB+ desktop application. An online KML viewer works instantly in any browser — no download, no admin rights, no IT approval needed.
Works on any device. Open KML files on Windows, macOS, Linux, or a Chromebook without compatibility concerns.
Access to raw attribute data. GeoDataTools exposes feature properties in a structured table and interactive popups, making it easy to read and analyze attribute data that is buried deep in Google Earth's interface.
Export and convert. Google Earth does not let you export to GeoJSON or CSV directly. GeoDataTools does, in one click.
Filter features. Need to isolate specific features from a large KML? GeoDataTools supports attribute-based and geometry-based filtering that Google Earth does not offer for quick ad-hoc queries.
Privacy. Your file is processed entirely client-side. No data is sent to any server, logged, or stored anywhere. This matters when working with confidential survey data, proprietary boundary files, or sensitive location information.

Common KML Viewing Issues and Fixes

If you run into problems opening or viewing a KML file, here are the most common causes and solutions:

File appears blank or empty on the map. The KML may use coordinates in a non-WGS 84 coordinate system. KML is supposed to use longitude/latitude in WGS 84, but some exports from older GIS software use projected coordinates. Check the source of the file and re-export with the correct CRS if possible.
Features appear in the wrong location. Verify that the coordinate order in the file is longitude,latitude — KML uses this order, which is the opposite of the common lat,lng convention. Some tools mistakenly write coordinates in the wrong order.
KMZ file fails to load. Some KMZ files contain multiple KML documents or have non-standard internal structures. Try renaming the file with a .zip extension, extracting it manually, and loading the inner .kml file directly.
Properties are missing. KML files can store attributes in ExtendedData, in description HTML, or in custom schemas. If attribute data looks incomplete, the original KML may be using a schema format that requires additional parsing.
Very large files load slowly. KML files with tens of thousands of features can be slow to parse and render. Consider splitting the dataset or filtering features before loading if performance is an issue.

FAQ

Is GeoDataTools really free to use as a KML viewer?

Yes. GeoDataTools is completely free to use for viewing KML files online. There is no account required, no usage limit, and no watermark on exported files. The tool runs entirely in your browser.

Does my KML file get uploaded to a server?

No. GeoDataTools processes your KML file entirely in your browser using Web Workers. Your file never leaves your device and is never transmitted over the network. This makes it safe to use with sensitive, confidential, or proprietary geographic data.

Can I convert my KML file to GeoJSON online?

Yes. After loading your KML file in GeoDataTools, use the export option to download a GeoJSON file, or use the dedicated KML to GeoJSON converter for a streamlined single-purpose workflow. The resulting GeoJSON file is standards-compliant and ready to use in any web mapping library or geospatial API.

How to View KML Files Online for Free (No Download Required)