File Extension CRDOWNLOAD is used by Google Chrome to temporarily store downloaded file information when file is being downloaded. Usually information in CRDOWNLOAD file is incomplete until file is downloaded.

QFX file extension is a open financial exchange file generated by Quicken. It is used to store financial information. QFX files are based on XML format and usually contain financial transactions for certain accounts.

A file with the extension .dmg (an abbreviation for disk image) uses a disk image format commonly found on Mac OS X. The format allows secure password protection as well as file compression and hence serves both security and file distribution functions.

KML files are very often distributed as KMZ files, which are zipped KML files with a .kmz extension. When a KMZ file is unzipped, a single doc.kml is found along with any overlay and icon images referenced in the KML.

ICA is a file extension used by Citrix Client files. They are used by Citrix client applications to connect to Citrix XenApp, Citrix XenDesktop and other Citrix server applications.

XPInstall (Cross-Platform Install) is a technology used by the Mozilla Application Suite, SeaMonkey, Mozilla Firefox, Mozilla Thunderbird and other XUL-based applications for installing Mozilla extensions that add functionality to the main application. A XPI (pronounced 'zippy' and derived from XPInstall) installer module is a ZIP file that contains an install script or a manifest at the root of the file, and a number of data files.

The AAE file extension is associated with the latest format of sidecar XML files, introduced in Apple iOS 8 devices (iPhone 5 and later) and Mac OS Yosemite to support non-destructive image / video editing including effects. The .AAE files are located next to the corresponding image files.

APK extension is used to deliver and install application software and middleware onto Google Android system. APK file contains compiled Android application code and all resources which are required by this code.

The existence of two different file extensions for naming audio-only MP4 files has been a source of confusion among users and multimedia playback software. Since MPEG-4 Part 14 is a container format, MPEG-4 files may contain any number of audio, video, and even subtitle streams, making it impossible to determine the type of streams in an MPEG-4 file based on its filename extension alone. In response, Apple Inc. started using and popularizing the .m4a file extension. Software capable of audio/video playback should recognize files with either .m4a or .mp4 file extensions, as would be expected, as there are no file format differences between the two. Most software capable of creating MPEG-4 audio will allow the user to choose the filename extension of the created MPEG-4 files.

JAR files are used to store java application libraries. JAR files are derived from ZIP files and use same compression mechanism. JAR files include a Java-specific manifest file