The File Extensions Database

.DEF File Extension

  • Developer by: Elecbyte
  • Category: Game Files
  • Format: Text

What is an .DEF file?

.DEF is M.U.G.E.N. Character Definition File

Game data file used by M.U.G.E.N., a sprite-based game engine used for making 2D fighting games; contains the definition for a character, including the character name and version information and the character specification files (.CNS, .SFF, .CMD, and .AIR) used by the engine.

Programs that open M.U.G.E.N. Character Definition File
Elecbyte M.U.G.E.N.
File Type 2 Module-Definition File
Category: Developer Files

Lists the exports and attributes of a program to be linked by an application linker; used in software development when creating a DLL.

DEF files are used by Microsoft Visual C++, a component of Microsoft Visual Studio, as well as other C++ development software.

Programs that open Module-Definition File
Microsoft Visual Studio 2017
File Type 3 SmartWare II Data File
Developer by: SmartWare Category: Spreadsheet Files

Spreadsheet and database format used by SmartWare II database software.

File Type 4 IOBit Malware Fighter Definitions File
Developer by: IObit Category: Data Files Format: Binary

File used by IObit Malware Fighter, a program used for removing malware and spyware from the PC; saves virus definitions used for identifying and removing malware from the computer.

DEF files use the filenames core000.def, core001.def, core002.def, etc. They are stored in the \db\ directory of the IObit Malware Fighter installation.

Programs that open IOBit Malware Fighter Definitions File
IObit Malware Fighter

How to solve problems with DEF files

  • Associate the DEF file extension with the correct application. On :
    Windows: Right click on any DEF file and then click "Open with" > "Choose another app". Now select another program and check the box "Always use this app to open *.DEF files". Mac: Right click (or Ctrl-click) the DEF file, then click "Open with" > "Other...". Then choose another program and check the "Always Open With" box. Linux: Right click on the file, and select "Open with" and choose another program. iPhone: Tap the file. If you do not see an app to open the file, then tap Share "Share" and choose an app. Alternatively, save the file. Then open the Files app Files app. There long-press on the file, then release your finger. You will see a black menu bar. Then tap "Share" and select an app. Android: Tap the Settings icon on your smartphone, then tap on the Apps section. There tap the Options icon in the top right-hand corner of the screen to change the default apps.
  • Update your software that should actually open .DEF is M.U.G.E.N. Character Definition File. Because only the current version supports the latest DEF file format. Search, therefore, e.g. on the Elecbyte manufacturer website after an available .DEF is M.U.G.E.N. Character Definition File update.
  • To make sure that your DEF file is not corrupted or virus-infected, get the file again and scan it with antivirus software.