.DEF File Extension
M.U.G.E.N Character Definition File
| Developer | Elecbyte |
| Popularity |
3.9 | 55 Votes |
What is a DEF file?
A DEF file is a game data file used by M.U.G.E.N (or just Mugen), a free sprite-based game engine used for making 2D fighting games. It contains the definition for a character, which includes the character name and version information. DEF files also store the character specification files (.CNS, .SFF, .CMD, .SND, and .AIR) used by the engine.
More Information
You will most likely only encounter a DEF file if you create games with the M.U.G.E.N engine. DEF files that store information for characters are located in the chars/ directory, while DEF files that store system-related information are located in the data/ directory.
Common DEF Filenames
[character_name].def - DEF file that stores information for a specific character.
fight.def - DEF file that stores information about the appearance of a fight in the game.
select.def - DEF file that stores a list of characters and stages available to select in a game, as well as the flow of the game's arcade mode. You can edit this file to add custom characters and stages to a game.
system.def - DEF file that stores information about the appearance of system screens, such as character selection and title screens.
How to open a DEF file
While DEF files are referenced by M.U.G.E.N and are not meant to be opened, you can open DEF files with a text editor since they are saved in plain text. Some text editors you could use in Windows are Microsoft Notepad and Microsoft WordPad. In macOS, you can use Apple TextEdit.
Programs that open or reference DEF files
Module-Definition File
| Developer | N/A |
| Popularity |
3.9 | 39 Votes |
Lists the exports and attributes of a program to be linked by an application linker; used in software development when creating a DLL.
More Information
DEF files are used by Microsoft Visual C++, a component of Microsoft Visual Studio, as well as other C++ development software.
Programs that open DEF files
SmartWare II Data File
| Developer | SmartWare |
| Popularity |
3.8 | 19 Votes |
A DEF file may also be a data file used by SmartWare II, a discontinued database and office productivity suite. It contains structured data that SmartWare II displays in tables, lists, or forms, allowing users to manage and view records and other entries.
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SmartWare is an office suite with database, word processor, and spreadsheet programs. It was initially developed in the 1980s for MS-DOS and Unix, and later Microsoft Windows, and used in office environments. It is now discontinued.
Programs that open DEF files
IOBit Malware Fighter Definitions File
| Developer | IObit |
| Popularity |
3.6 | 11 Votes |
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.
More Information
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 or reference DEF files
WWE 2K18 and 2K19 PAC Pointer File
| Developer | Yuke's |
| Popularity |
1.0 | 2 Votes |
A DEF file may also be a game data file used by WWE 2K18 and 2K19. It contains pointers to the .PAC files the games load at startup. The games' DEF file is named Chunk0.def.
More Information
WWE 2K is a series of popular video games based on the WWE pro wrestling franchise. WWE 2K14 to 2K19 were developed by Yuke's.
2K18 and 2K19 use an index file named Chunk0.def to note what PAC asset archives they should load at startup. This file is a plain text file, which most players will never need to open or edit. However, WWE 2K18 and 2K19 modders who have added custom PAC files to the games must add a reference to those PAC files to Chunk0.def. Otherwise, the games will not load the custom PAC files.
NOTE: Other Yuke's-developed WWE 2K games do not use a DEF file.
Common DEF Filenames
Chunk0.def - The DEF file included with WWE 2K18 and 2K19.
How to open a DEF file
You can open and edit Chunk0.def with Microsoft Notepad (Windows) or any other text editor. Some WWE 2K modding tools, such as Custom Character Tools 2019 and Custom Character Tools 2018, allow modders to automatically update Chunk0.def after they've added a custom PAC to the games.