DEF - C++ Module-Definition File

What is a DEF file

Files that have the DEF extension can be associated with several programs. One of the most common is Microsoft Visual Studio, and more precisely, Microsoft Visual C++. Other C++ development programs can create DEF files as well though.

DEF files are saved in a plain text format which allows them to be opened in any text editor across different operating systems. The DEF file lists different attributes of a program in order for an application linker to be able to correctly link them. These files are mostly used when creating DLL files in software developing.

Here's a small, but not exhaustive list of programs that can open DEF documents:

  • Microsoft Visual Studio (Windows)
  • Any Text Editor
Extension DEF
MIME type text/plain
Useful links