KML and KMZ viewer

How to use it

Drag the file onto the tool or pick it with the button. Right away you’ll see it on the map with its own colors, along with how many points, lines and polygons it has, the length of the lines and the area of the polygons. Tap a feature on the map or in the list to see its name, description and all of its data.

The file is read in your browser and isn’t uploaded anywhere. You can open a KML with private data, like the fields on a farm or the stops on a sales route, and it never leaves your device.

What a KML file is

KML (Keyhole Markup Language) is Google Earth’s file format. It comes from Keyhole, the company Google bought in 2004 to build its virtual globe, and in 2008 the Open Geospatial Consortium (OGC) adopted it as a standard. It’s an XML text file that stores placemarks (points, lines and polygons), folders, styles and data for each feature.

Coordinates in a KML are always longitude, latitude and, optionally, altitude, on the WGS84 datum used by GPS. That’s why a KML opens the same way everywhere: Google Earth, Google My Maps, QGIS, ArcGIS or this viewer.

KML vs. KMZ

A KMZ is a KML zipped up, sometimes together with the icons and images it uses. It’s much smaller, which is why Google My Maps and Google Earth usually export KMZ. This viewer unzips it in your browser and opens the main KML inside, usually “doc.kml”.

If an app asks for a KML and you have a KMZ, open it here and download it as KML. If a KMZ won’t open, check it isn’t a shapefile or a ZIP with something else inside: the viewer will tell you.

How to get a KML out of Google My Maps or Google Earth

In Google My Maps, open the three-dot menu next to the map title and choose “Export to KML/KMZ”. You can export the whole map or a single layer, and tick the box to get a KML instead of a KMZ. Each layer comes out as a folder, and the columns of the data table as data for each feature.

In Google Earth Pro, right-click a folder or a place in the list and choose “Save Place As…”. You can save it as KML or KMZ.

Common problems when opening a KML

Nothing shows up on the map. The KML may only hold a network link (NetworkLink) to another file online, which isn’t followed, or an image overlay (GroundOverlay). The viewer tells you about both. The coordinates may also not be in degrees because a GIS program wrote the file wrong: in that case the viewer asks which system they’re in.

The icons don’t look like Google Earth’s. Points are drawn as circles in their icon’s color, and lines and polygons with their own color, width and transparency. Descriptions with HTML are shown as plain text, so nothing in them runs.

Many KML files set the altitude to 0 for every point. The viewer drops it when reading the file so it doesn’t end up in a GPX or CSV looking like a real elevation.

Converting a KML to GeoJSON, GPX or CSV

Names, descriptions, each feature’s data (ExtendedData), folders and styles all carry over. In GeoJSON, folders go in a “folder” property and colors use the simplestyle keys that geojson.io and many other tools understand. In GPX, points become waypoints and lines become tracks; polygons become closed tracks, because GPX has no polygons.

The CSV has one row per feature with its geometry as WKT, the column QGIS and Google My Maps read on import, or one row per point, with its elevation. If you open the converted file here again, everything is back the way it was.