BSI File

What are BSI files and how to open them

Are you having problems opening a BSI 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 BSI files.

What is a BSI file?

BSI files have multiple uses, and Bethesda Image Texture is one of them. Read more about the other uses further down the page.

Bethesda Image Texture

Bethesda Image Texture files store 8-bit indexed graphics used in the games Battlespire and Redguard by Bethesda Softworks. These textures are used for 2D surfaces such as wall panels, menu graphics, sprites or decorative elements rather than 3D mesh materials. The images may include animations (multiple frames) and utilize embedded or external palettes for color lookup and transparency.

These files are created by Bethesda (or tools working with their assets) and read by the game engine or modding tools for Redguard and Battlespire. They are not edited by external tools in format-aware mode, since structure - including the headers, palettes, and chunked image data - is specific and usually only read (loaded), not written. Modders reverse-engineered parts of the format via libraries such as the Vampyre Imaging Library, which supports decoding these files.

Internally the format is organized in a chunked structure similar to PNG: there is a TTextureBSIHeader at the start (for "multi-BSI" Redguard files), followed by chunks with 4-character IDs such as IFHD or BSIF, BHDR, HICL, HTBL, CMAP, DATA, END. The BHDR chunk holds main image metadata (such as width, height, frame count), CMAP contains the palette, and DATA holds the pixel indexes. Redguard files sometimes contain multiple images in one file; Battlespire ones appear to support animation and a blue-channel mapping table. Signature checks typically test for "IFHD" or "BSIF" early in the file.

How to open BSI files

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

While we have not verified the apps ourselves yet, our users have suggested nine different BSI openers which you will find listed below.

Last updated: August 25, 2026

All known file formats using extension .BSI

While Bethesda Image Texture is a popular type of BSI-file, we know of 2 different uses of the .BSI file extension. Different software may use files with the same extension for different types of data.

Future Composer (BSI) Module

Future Composer (BSI) Module files are music tracker modules produced by the Amiga program Future Composer. They hold song data including patterns, instrument or synthetic sound definitions, block ordering, playback speed, and may use both real sample data and short synthetic samples for effects such as vibrato etc.

These modules are created by the Future Composer editor, which was developed in the Amiga's scene/demoscene era, notably by Jochen Hippel. They use multiple voices/tracks tied to the Amiga's audio hardware to play back patterns and blocks. Some versions are numbered (1.0-1.3, 1.4 etc.), and module creators include both synthetic and sampled sound content.

Byte signatures include the ASCII string "FUCO" at offset 0, followed by other metadata inside, and the presence of the string "DIGI" somewhere inside the file. These help distinguish Future Composer (BSI) Module files from other formats.

Various apps that use files with this extension

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

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 BSI file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.