.def file: how to open it on Windows

4 Windows apps register the .def extension. Install one of them to open the file with a double-click.

About the format

Format

ESRI Arc/View Project

PRONOM identifier

fmt/332, fmt/1163

Format data: freedesktop.org shared-mime-info and PRONOM (The National Archives, UK).

• 
  DMD

  DMD Compiler for Windows

  Open source 2.113.0 24.8K ↓
• P
  PSPad editor (x86)

  The Developer’s Text Editor for Microsoft Windows

  Free 5.5.2.851
• P
  PSPad editor (x64)

  The Developer’s Text Editor for Microsoft Windows

  Free 5.5.2.851
• T
  Text Editor Pro

  Powerful text editing tool

  Free 37.4.0

Related guide: Change the default app for a file type in Windows