BW File

What are BW files and how to open them

Are you having problems opening a BW 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 BW files.

What is a BW file?

BW files have multiple uses, and bigWig Track Format is one of them. Read more about the other uses further down the page.

bigWig Track Format

These BW (BigWig) files contain the genome data that will be displayed in the Genome Browser, a web-based tool used to display a requested portion of a genome at any scale. These genomes are gene predictions like mRNA, phenotype, multiple-species comparative genomics data, etc. These BW files have a faster display performance when working with large data files. These files are stored/displayed on your local web-accessible servers like HTTP or FTP.

How to open BW files

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

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

Last updated: August 5, 2026

All known file formats using extension .BW

While bigWig Track Format is a popular type of BW-file, we know of 3 different uses of the .BW file extension. Different software may use files with the same extension for different types of data.

Raw Black And White Bitmap

We know that one BW format is Raw Black And White Bitmap. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

BW opener for Windows

We have identified one BW opener that is compatible with this specific type of BW file.

Silicon Graphics B/W Bitmap

Silicon Graphics B/W Bitmap is a monochrome image file used on SGI (Silicon Graphics) workstations to store single-channel black-and-white or greyscale images. It is part of SGI's native image file family, which also includes .RGB (color), .RGBA (color with alpha), .INT (plane-based integer image), and other variants. Files with the .bw extension are created when image data has just one channel (no color) and are useful for storing greyscale or strictly black & white content.

Files are written by graphics tools and systems that support the SGI Image Format - on IRIX and related high-end Unix or workstation platforms, or by cross-platform image libraries that include SGI support (such as ImageMagick or PMView). When you use such a tool to save a monochrome image in the SGI format with one channel, it will write it as a .bw file. Other tools that open SGI formats (with one channel) also read .bw files.

Technically the file begins with a big-endian header where the first two bytes form the magic number 0x01DA, followed by fields for compression type (uncompressed or run-length encoded), bytes per channel (typically 1 or 2), image dimensions, number of channels (one for .bw), and other metadata including the color map identifier.

Programs that open these BW files

We have identified one BW opener that is compatible with this specific type of BW file.

Various apps that use files with this extension

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