A file with .bns extension is a game script file created with Portal Map puzzle solving game that was developed by Valve. It contains text script for defining information about a Portal map which is stored as .bsp file. BNS files are used as reference to this actual map file and contains a list of challenges that are to be completed. In addition, it contains map name, comments about the map, and thumbnail image file references. A BNS file can be opened in any text editor such as Notepad++, textEdit, and Notepad.
BNS File Format
BNS files are saved as plain text files that are human readable. These can be opened in text editors and edited as well. However, these should be carefully edited to avoid any errors in the script.
BNS File Format Example
A BNS file may look something like the following when it is opened in a text editor such as Notepad++.