What is a .EXTR file?
An .EXTR file is a special kind of folder that is used by something called COW. COW was supposed to be a new way for some mobile phones to work, kind of like how iPhones use iOS and some other phones use Android. But, COW was based on Linux, which is another system that computers can use to run. The thing is, COW was never actually finished or given to the public to use.
Inside an .EXTR file, there's a program and a special file named Main.py. This Main.py file has instructions that tell the COW system how to put the program onto the phone properly. When someone using COW wanted a new app, they would get these .EXTR files from the COW App Store. Once downloaded, the COW system on the phone would automatically open this .EXTR file, understand the instructions, and install the app as needed.
However, you can't really open .EXTR files by yourself. They were designed to be opened automatically by the COW system on the phone, not by people. Plus, since COW was never actually released, you're not likely to see these .EXTR files around. If you do find a file that ends in .extr, it's probably not related to the COW system at all and is something entirely different.
Verification
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