Known DEF Files

Leading DEF Type

.DEF

Extension:	.def
File Type:	Module Definition File

Module definition file contains various settings, provides the linker with information about exports, attributes, and other information about the program to be linked.

Author:	Microsoft Corporation
File Category:	Developer Files
Location:	HKEY_CLASSES_ROOT\.def

Software Programs That Open The Module Definition File:

Microsoft Visual Studio by Microsoft Corporation

Windows

Microsoft Visual C++ by Microsoft Corporation

Windows

Other DEF Descriptions

.DEF

Extension:	.def
File Type:	SmartWare II Data File

DEF file is a spreadsheet file created by SmartWare II software, a set of database, spreadsheet with graphics, word processor, and communication applications for Windows.

Author:	SmartWare Corporation
File Category:	Spreadsheet Files

Software Programs That Open SmartWare II Data File Files:

SmartWare II by SmartWare Corporation

Compatible with:

Windows

.DEF

Extension:	.def
File Type:	M.U.G.E.N. Character Definition File

Definition for a character, including the character name, version information and other data. DEF files associated with M.U.G.E.N., a sprite-based game engine used for making 2D fighting games.

Author:	Elecbyte
File Category:	Game Files

Software Programs That Open M.U.G.E.N. Character Definition File Files:

Elecbyte M.U.G.E.N by Elecbyte

Compatible with:

Windows

Mac

Linux

.DEF

Extension:	.def
File Type:	IOBit Malware Fighter Definitions File

Virus definition file used for identifying and removing viruses. DEF files are used by IOBit Malware Fighter, an application able to detect and remove malware from PC.

Author:	IObit
File Category:	Data Files

Software Programs That Open IOBit Malware Fighter Definitions File Files:

IObit Malware Fighter by IObit

Compatible with:

Windows

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DEF File Complications

Common Problems Opening DEF Files

Microsoft Visual Studio Not Present

Double-clicking your DEF file prompts the message "%%os%% Can't Open DEF File". When this happens, it is commonly due to Microsoft Visual Studio missing in %%os%%. The OS won't know what to do with your DEF file, so double-clicking to load the file doesn't work.

Tip: If you don't have Microsoft Visual Studio installed, and you know of another program to open your DEF file, you can try opening it by selecting from the programs listed under "Show Apps".

Microsoft Visual Studio is Out-of-Date

Sometimes your installed version of Microsoft Visual Studio won't support your Module Definition File file. You will need to download a newer version of Microsoft Visual Studio if you don't have the right version. Your Module Definition File file was probably created by a newer release of Microsoft Visual Studio than what's currently installed your computer.

Tip: Right-clicking on your DEF, then clicking "Properties" (Windows) or "Get Info" (Mac), can provide clues about your file version.

Regardless, most of the DEF file opening problems relate to not having the right version of Microsoft Visual Studio installed.

Other DEF File Opening Causes

Errors opening Module Definition File files can still occur even with the latest Microsoft Visual Studio software installed on your computer. If you are still having problems opening DEF files, there may be other issues that are preventing you from opening these files. Problems unrelated to software:

• Windows Registry DEF file paths that are incorrect
• Accidental deletion of the description of the DEF file in the Windows registry
• Defective install of a DEF program, such as Microsoft Visual Studio
• Something has caused file corruption of your DEF
• Your DEF has adversely impacted by malware
• Hardware associated with DEF has outdated drivers
• Windows cannot load your Module Definition File file due to insufficient resources (eg. RAM)