Unfortunately, there isn't one simple answer to what a bro file is because there are no rules, laws, or copyrights regulating the use of file extensions. Consequently, many programs create bro files or save data in a bro file format for differing reasons and purposes. However, there are some common uses for the bro file extension and common ways to convert bro files of the appropriate type to a different file format.

Bro files are regularly created by a program called Tree Professional Broadleaf Creator or OnyxTREE Broadleaf depending on the version. This program is a 3D modeler used for creating trees and bushes. A bro file created by this software can only be opened by this software, but the software can save its models in a variety of formats making it able to be opened by other software.

Some Roland/Boss digital recording hardware devices record audio tracks in bro file format. Roland offers conversion software called BR Wave Converter which can convert these bro files into more common audio formats such as .wav or .aiff or convert common audio file formats into bro file format to be usable on their hardware devices. This software can be downloaded from Roland's website.

Embroidery and stitch files created by Bits and Volts software are saved in the bro file format. A number of more common computerized embroidery programs can read and convert these files.

Broderbund's Create a Booklet/Brochure Project software saves brochures with the bro file extension.

Bro, an open-source network intrusion detection system based in Unix, uses the bro file extension for internal policy scripts. There is no reason to convert these files because they contain information that is only relevant to this specific software.

Because of the lack of restriction on file extensions, any number of other programs could create files with this extension, but this list covers the most frequent ways a file is saved in this format.