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List of common system file extensions
You can encounter these files in various operating systems. You should not try to alter or delete any of these files unless you know what you are doing.
Common system file types may change in time as the popularity and significance of some formats can change.
Whole category of system file types contains now 481 file types. Show all system file types.
| alx | An alx file extension is used for files that contain data used for installation of apps to BlackBerry smartphones. ALX is text format viewable in every text editor. |
 blf | Files with blf file extension are commonly found as temporary files generated by latest Windows operating system to prevent registry corruption whenever a change to registry is done. |
 cpl | Files with cpl file extension are most notably known to be control panel applets from Microsoft Windows operating system. Each control panel is represented by a single .cpl file. |
| dat | Files with dat file extension are commonly found in a variety of applications and in most cased used to identify files that contain application data resources or similar data. |
 dll | Files with dll file extensions can be commonly found as dynamic link libraries for Microsoft Windows systems and apps. These files act as modules with additional runtime routines or data. |
 drv | Files with drv extension are commonly found as device drives, especially in older versions of Windows operating system. Used for system purposes. |
 ds_store | Files with ds_store extension can be typically found by Mac OS X (macOS) users in many of their folders. These files contain information about various folder and window settings. |
| dump | Files with dump extension can be usually found as various dump files generated by programs when some error is encountered in the system. Used for analysis of the errors to help troubleshoot it. |
 evtx | Files with evtx extension can be usually found as event logs generated in Microsoft Windows operating system. An event log file contains various information how programs are working, and type of errors they encounter. |
A gadget file extension is used for Windows Gadgets, small programs that enhance the desktop with various features. Gadgets are usually located in the Windows Sidebar, on the right side of desktop. | |
| idx | Files with idx extension can be usually encountered as various index files from all kind of programs and applications. |
 inf | Files with inf file extension can be generally found as various installation scripts in Microsoft Windows operating system. |
 kext | Files with kext file extension can be commonly found as system files in Mac OS X (macOS) operating system. Kernel files. |
 key | Files with key file extension can also be found as registry entries for o Microsoft Windows operating system. |
 mui | Files with mui extension are mainly related to Microsoft Windows are used for language packages with which you can add the default localization of your OS. |
 ocx | Files with ocx extension are associated with the Microsoft ActiveX Control items. An ocx is an OLE custom control (program) that is used by various Windows applications to provide such function as handling scroll bar movement and window resizing. |
 reg | Files with reg extension can be usually found as Windows registry files, special files that contain exported registry entries that can be uploaded to the system. |
| rom | Files with rom extension can be most often found as various ROM (read only memory) images, either for emulation purposes or for updating firmware / BIOS. |
 scr | Files with scr extension can be most typically found as screensavers for Microsoft Windows operating system. However, never open random .scr files from untrustworthy sources. |
 sfcache | Files with sfcache extension are used for Microsoft Windows ReadyBoost cache files. They are stored on flash memory device (USB flash, SD card, CompactFlash etc.) and generally used to faster random disk reads that speed up a computer. |
| swp | Files with swp file extension can be commonly found as various swap files generated by operating systems or programs for memory paging purposes. |
| sys | Files with sys file extension can be often found as various system files in DOS / Windows and other operating systems. They contain information needed to properly load and configure operating system. A corrupted or missing system file can cause the system to be unstable or unable to boot. |
 vxd | Files with vxd file extension can be mostly found as virtual device drivers from Microsoft Windows operating system. |
This is a list of some the most common file types from this category and may change in time as the popularity and significance of some formats can change. Whole category of system file types contains now 481 file types. Show all system files.
