Which MIME types are related to file extension ".cmpt"?
The .cmpt file extension is associated with 3 MIME types:
application/json, application/octet-stream, application/vnd.maxar.archive.3tz+zip.
A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.
About .cmpt Files
CMPT files are a 3D Tiles archive file format. They combine multiple 3D tile assets into a single package.
This format often carries both structured text and binary data. For instance, application/json is used for metadata, while application/octet-stream holds binary components. Additionally, application/vnd.maxar.archive.3tz+zip indicates a zipped archive tailored for 3D Tiles data.
- Main Use: Packaging and transferring 3D mapping tiles.
- Key Fact: It includes both human-readable and machine-readable data.
- Supported Software: Specialized geospatial programs, 3D viewers like Cesium, and GIS applications.
- Practical Note: The mixed MIME types point to a composite file that manages complex spatial data efficiently.
Relationship between file extension and MIME type
A file extension is a suffix at the end of a filename that indicates what type of file it is. File extensions help both users and operating systems identify what application should be used to open the file.
File extensions are typically separated from the filename by a period (dot) and consist of 2-4 characters, though they can be longer. For example, in the filename "document.pdf", ".pdf" is the file extension.
File extensions are closely related to MIME types, as they both serve to identify the format of a file. However, while MIME types are used primarily by web browsers and servers, file extensions are used by operating systems and applications.
Associated MIME types
application/json, application/octet-stream, application/vnd.maxar.archive.3tz+zip
FAQs
What is a .cmpt file?
A .cmpt file is a Composite Tile format defined by the OGC 3D Tiles specification. It allows multiple tile contents (such as Batched 3D Models or Instanced 3D Models) to be concatenated into a single binary file for efficient streaming in geospatial applications like CesiumJS.
How do I open or view a .cmpt file?
You cannot open this file with a standard image viewer or text editor. To view the 3D content, you need a compatible 3D Tiles viewer such as CesiumJS, Unreal Engine (with Cesium plugin), or specialized GIS software capable of rendering Composite Tiles.
Can I convert .cmpt files to other 3D formats?
Yes, but it usually requires a two-step process. First, use command-line utilities like 3d-tiles-tools to extract the inner tiles (e.g., .b3dm or .i3dm) from the composite file. Once extracted, those individual files can often be converted to standard formats like glTF (.gltf or .glb) for use in tools like Blender.
Why does the file contain both binary data and JSON?
The .cmpt format acts as a container; it has a binary header followed by the payloads of other tile formats. While the container is binary, the 3D Tiles ecosystem relies heavily on application/json for the metadata (tileset.json) that references these files, and the inner tiles themselves often contain JSON headers describing the geometry.
What MIME type should be configured for serving .cmpt files?
For web servers hosting 3D Tiles, .cmpt files are typically served as application/octet-stream because they are binary blobs. However, the associated tileset definitions must be served as application/json. For more details on MIME configuration, visit mime-type.com.
Is a .cmpt file an archive like ZIP?
Conceptually, yes, because it packages multiple assets together, but technically, no. Unlike a standard ZIP file (associated with application/zip), a .cmpt file uses a specific binary concatenation method defined by the 3D Tiles spec, so you cannot open it with tools like WinZip or 7-Zip.
General FAQ
What is a MIME type?
A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.
MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.
MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.
How do I find the MIME type for a file?
You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.
Why can one extension have multiple MIME types?
Different programs and historical usage may assign various MIME identifiers to the same file format. Listing them together helps maintain compatibility across tools.