CHU File

What are CHU files and how to open them

Are you having problems opening a CHU 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 CHU files.

What is a CHU file?

A .CHU file is an Infinity Engine User Interface Description file.

Infinity Engine User Interface Description files define the layout of graphical user interface screens in classic games built on the Infinity Engine (such as Baldur's Gate, Icewind Dale, Planescape: Torment). They specify where windows appear, which interactive controls (buttons, labels, sliders, text entry boxes) are placed inside those windows, and reference external graphics for backgrounds or control images. The actual artwork (sprites, MOS or BAM files) is stored separately; these UI description files simply tell the game engine how to assemble those elements into usable menus, dialogs, and other interface screens.

The UI description format is created by game development tools used by BioWare or its licensors during the creation of Infinity Engine titles. Once authored, they are read by the running game to render menus, HUDs, options screens, dialog panels, and other interface elements. Modders and hackers also use documentation of this format to alter or extend UI screens.

Files begin with a signature string that identifies the format version (for example "CHUI" followed by version "V1 "). After the header, data includes a list of windows (each with position, size, background settings and control indices), followed by a table of individual control definitions. Controls have a shared base specifying position within its parent window, size, control type (with values like 0 for button, 2 for slider, 3 for text edit field, 5 for multiline text area, etc.), plus extra fields depending on control type such as references to external resources (graphics or fonts), animation cycles, initial text, maximum length, and other flags.

Byte signature for this version is the ASCII string "CHUIV1" at the start of the file (offset zero).

How to open CHU files

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

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 31, 2026

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CHU file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.