The d file extension is related to the Infinity Engine and used for its dialogue files.
D file extension - Infinity Engine dialogue file
What is d file? How to open d files?
File type specification:
The d file extension is associated with the Infinity Engine a video gaming engine for Baldur's Gate, IceWind Dale, Planescape Torment and other computer games developed by Bioware.
The *.d file stores in-game dialogues.
List of recommended software applications associated to the .d file extension
Recommended software programs are sorted by OS platform (Windows, macOS, Linux etc.) and possible program actions
that can be done with the file: like open d file, edit d file, convert d file, view d file, play d file etc. (if exist software for corresponding action in File-Extensions.org's database).
- Others d file
Unspecified and all other actions for computer programs working with d file - Infinity Engine dialogue file
Click on the software link for more information about Baldur's Gate. Baldur's Gate uses d file type for its internal purposes and/or also by different way than common edit or open file actions (eg. to install/execute/support an application itself, to store application or user data, configure program etc.).