BC File

What are BC files and how to open them

Are you having problems opening a BC 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 BC files.

What is a BC file?

BC files have multiple uses, and Big Crunch compressed is one of them. Read more about the other uses further down the page.

Big Crunch compressed file

These BC files contain data compressed by the Big Crunch compression tool. Big Crunch was an experimental data compression project developed by the four students Eric Chanudet, Jérémie Roquet, Nicolas Ballas, and Paul Baudron, released under the name "the KaBoom group" in the mid-2000s.

How to open BC files

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

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

Last updated: August 23, 2026

All known file formats using extension .BC

While Big Crunch compressed file is a popular type of BC-file, we know of 5 different uses of the .BC file extension. Different software may use files with the same extension for different types of data.

LLVM Bitcode

These BC files are LLVM (Low-Level Virtual Machine) Bitcode file formats used to store tags and nested structures. Bitcode uses binary encoding. Bitcode is similar to XML because you can parse the file without understanding what the tags mean.

LLVM Bitcode Data

These BC files contain program pieces compiled by a compiler based on the LLVM compiler infrastructure into its binary intermediary representation format. LLVM-based compilers can compile several different programming language source code files into program files. During compilation, which is the transformation process from human-readable source code into a machine-executable format, LLVM outputs the compiled instructions in this machine-independent bitcode format. Other tools are used to transform these binary pieces into runnable programs targeted to various platforms.

Photoshop Thumbnail Cache

Photoshop Thumbnail Cache files store small preview images and related information to help Adobe applications show thumbnails quickly when browsing folders of image files. These cache files are produced by Adobe Bridge (and earlier by Photoshop's File Browser tool) whenever a user views images; the application writes entries containing thumbnails, metadata (such as names, ratings or labels), and possibly 100 % previews to speed up later viewing. The cache makes folder contents display faster and reduces needing to regenerate previews each time.

These files are typically written invisibly; one configuration stores them centrally (in a shared cache location), while another mode called "distributed cache" places the cache files inside each image folder. Users can also tell Adobe Bridge to export cache files into folders for archiving or sharing so that thumbnails travel along when moving folders to another machine or medium. Purging or rebuilding the cache forces thumbnails and metadata to be regenerated.

The signature at the very start of the file is the ASCII string "hcac" (bytes 0x68 0x63 0x61 0x63) at offset zero, which identifies it as a Photoshop Thumbnail Cache file.

SPICE Binary CK

SPICE Binary CK files store orientation (attitude or pointing) data for spacecraft structures or scientific instruments. They are part of the SPICE Toolkit developed by NAIF (NASA's Navigation and Ancillary Information Facility). The key role of this format is to give, for given times, precise attitude information - usually transformation matrices (C-matrices) and optionally angular velocity vectors - relating an instrument-fixed coordinate frame to a standard reference frame. These files are essential for modeling where an instrument was pointing at different times, and for combining attitude with other trajectory and time data to derive observation geometry.

SPICE Binary CK files are produced by NAIF tools when computing or encoding pointing data. They are loaded by SPICE library routines (e.g. CSPICE) in applications that compute observation geometry, for example, mapping, instrument calibration, or science data reduction. Users do not manually edit them: the content comes from processed telemetry, attitude control system outputs, or derived attitude models. When an application asks for pointing at a certain time, the toolkit locates the right "segment" inside the CK, interpolates or retrieves the attitude (C-matrix), and returns it.

These files are built using the DAF architecture - Double Precision Array File. Every CK file is a DAF file whose segments are arrays of double-precision data. There is a comment area in each file for storing ASCII documentation such as epochs covered, instrument codes, accuracy estimates, and information about data sources. Binary CK files include an identification signature: the first eight bytes are the ASCII string "DAF/CK " (with spaces to pad to eight bytes).

Various apps that use files with this extension

These apps are known to open certain types of BC files. Remember, different programs may use BC 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 BC file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.