Sustainability of Digital Formats: Planning for Library of Congress Collections

KMZ is the ZIP-compressed KML (formerly Keyhole Markup Language) file that stores map locations viewable in various geographic information systems (GIS) applications, such as Google Earth, Blue Marble Geographics’ Global Mapper, and/or ESRI ArcGIS Pro. It contains one or more placemarks that may include a custom name and the latitudinal and longitudinal coordinates of the location. KMZ files may also include COLLADA 3D models, overlays, sound files, textures, and images referenced by the KML file. The structure of KMZ files are defined by the Open Geospatial Consortium as part of the KML specification in Annex C. See KML for more details about KML files and structure.

KMZ files consist of a main KML file and zero or more supporting files that are packaged using a ZIP-compression utility into one unit, called an archive. KMZ files may then be stored, shared by email, or hosted on a web server. A NetworkLink can fetch a KMZ file from a web server. When the KMZ file is unzipped, the main KML file and its supporting files are separated into their original formats and directory structure, with their original filenames and extensions.

In addition to being an archive format (also known on this site as an Aggregate format), the ZIP format is also compressed, so an archive can include only a single large KML file. Depending on the content of the KML file, this process typically results in 10:1 compression. For example, 10 kilobyte KML file can be served with a 1 kilobyte KMZ file.

A KMZ file contains a single root KML document, typically a file named "doc.kml" at the root directory level but the first .kml file entry in the KMZ file is the actual one selected in Google Earth regardless of its name. Files for referenced overlays, images, icons, etc., including network-linked KML files, can be included. Referenced files are typically in subdirectories. To be compatible with all geobrowsers, the ZIP file should use no compression or DEFLATE compression (i.e. be compatible with the 1993 PKWARE 2.0 version of the ZIP specification, as registered with IANA).

A single KMZ file may not be complete because KMZ supports dynamic incorporation of remote KML data not included in the file. This feature is useful to reduce bandwidth during real-time use.

Google designed KMZ files to reduce the space taken up by KML files, allow for supporting files, and to make them easier to distribute and share with multiple users. See KML.

Common uses for KMZ files include sharing placemarks or tours with users via email or when publishing on a webpage. Various programs may create KMZ files, but Google Earth Pro primarily creates the files.

Users can open KMZ files with various mapping applications for Windows, macOS, Linux, Android, and iOS. The Google Earth Pro desktop application is a common choice for opening KMZ files. Files can also be opened in Google Maps by saving the KMZ file to an online location and then typing the URL in the Google Maps search box.

Since KMZ files are ZIP-compressed KML files, they can also be opened by changing the .kmz file extension to .zip, then decompressing them with a ZIP utility. The resulting KML file can then be opened with a GIS application.

KMZ files, zipped KML files with a .kmz extension, contain a single root KML document (notionally "doc.kml") and optionally any overlays, images, icons, and COLLADA 3D models referenced in the KML including network-linked KML files. KML documents and their related images (if any) may be compressed using the ZIP format into KMZ archives. KML documents and KMZ archives may be shared by e‑mail, hosted locally for sharing within a private internet, or hosted on a web server.