Converting KML to KMZ compresses a plain-text Google Earth document into a smaller, single-file ZIP package.
What is KML?
KML (Keyhole Markup Language) is an XML-based format for expressing geographic annotation and visualization, adopted as an OGC standard and popularized by Google Earth.
KML describes Placemarks, geometries (points, lines, polygons), and their presentation using an XML tree that also supports folders for organization, rich styling (icons, colors, line widths, fills), balloon descriptions, and ground overlays. It is designed for display and sharing rather than analysis, and is opened natively by Google Earth, Google Maps, and most GIS packages. Because it targets a single global view, it has no concept of reprojection.
What is KMZ?
KMZ is a ZIP archive that packages a KML document (conventionally named doc.kml) together with any assets it references, such as icons, images, and overlays.
Structurally a KMZ is just a compressed container: unzip it and you get a main doc.kml plus an optional folder of supporting files. Zipping typically shrinks verbose KML text substantially and keeps a placemark set and its custom icons together as one shareable file, which is why Google Earth exports KMZ by default. Everything true of KML applies to the KML inside a KMZ; the wrapper only adds compression and asset bundling.
Why convert KML to KMZ?
KMZ is easier to share and email than raw KML because compression can shrink the verbose XML significantly. It bundles the document (and any referenced assets) into one portable file that Google Earth opens natively. This is the natural choice when file size or a single deliverable matters.
Coordinate systems
KML coordinates are always geographic WGS84 longitude, latitude, and (optionally) altitude in that order; the format has no CRS or projection field, so any data written to KML is expressed in EPSG:4326 by definition.
Because the payload is ordinary KML, a KMZ is inherently WGS84 (EPSG:4326) longitude/latitude/altitude, with no projection metadata and no possibility of reprojection inside the format.
What to watch out for
- This is essentially compression: a KMZ is just a ZIP wrapping the KML (as doc.kml), so no geometry or attributes change.
- Coordinates remain WGS84 (EPSG:4326); nothing is reprojected.
- The output is binary and no longer directly readable in a text editor.
- If the KML references external icons or images, only assets included in the archive travel with the KMZ.
How to convert KML to KMZ
- Drag your KML file (.kml) into the converter above, or click to browse.
- Confirm the source is KML and choose KMZ as the output format.
- Optionally pick a target coordinate system (EPSG) to reproject.
- Click Convert and download your KMZ file. Everything runs in your browser.
Frequently asked questions
- Does converting KML to KMZ change my data?
- No. It only compresses and packages the KML; geometry, attributes, and coordinates are unchanged.
- How much smaller will the file be?
- It varies, but KML is verbose XML that typically compresses well, so KMZ downloads are often much smaller.
- Can the KMZ be opened like a normal KML?
- Yes. Google Earth and most GIS tools read KMZ directly, and you can also unzip it to recover the doc.kml.