BDY File

What are BDY files and how to open them

Are you having problems opening a BDY file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BDY files.

What is a BDY file?

A .BDY file is a Chess Assistant Comments Bodies file.

Chess Assistant by ChessOK creates these files when storing or backing up commentary text attached to moves in games. They contain the full bodies of comments that have been entered during game analysis - such as detailed explanations, remarks, and annotations - separate from the game's move data. These files are used internally by Chess Assistant to keep comment texts organized and retrievable once referenced by the game's annotations index.

Chess Assistant writes these comment body files; they are not standalone game files but parts of its broader database system. When a game has comments, those comments are split: brief descriptors or references go into an index, while the longer text goes into this comment‐body file. When opening or browsing games in Chess Assistant, the program reads from these files to display the full comment text.

The file begins with an ASCII signature "Comments bodies. Chess Assistant Ver" at the very start (offset 0) to identify it as this specific format's comment bodies data.

How to open BDY files

Important: Different programs may use files with the BDY file extension for different purposes, so unless you are sure which format your BDY file is, you may need to try a few different programs.

While we have not verified the app ourselves yet, our users have suggested a single BDY opener which you will find listed below.

Last updated: August 23, 2026

Various apps that use files with this extension

These apps are known to open certain types of BDY files. Remember, different programs may use BDY files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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