This small 64 bit app displays an overview of file extension of all files in a chosen directory and all of its subdirectories. It can be run from the commandline and from GUI. It is tested with the current Qt-Creator 4.13.2 and Visual Studio Community 2019 on Windows 10 and with Qt-Creator 4.13.2 on Ubuntu 20.10. It uses only Qt data types, so it should run on Mac also. If you call it from command line, you can pass a directory as first (and only) parameter. If you call it without parameters, a file dialog appears, where you can specify the directory.
You can double click on a file extension and all directories holding files with this extension show up.
If you double click the directory, windows explorer is opened in this directory.
You can download the source code at https://github.com/artylan/dirext.
Or you can download the Windows-Installer here DirExtQtSetup.exe. If you install this, you get a context menu item „Run ExtDirQt“, if you click on a directory in explorer. So you can directly inspect a directory, without starting DirExtQt separately.
If you get an error after starting DirExtQt, then you have to install the Visual Studio Redistributables vc_redist.x64.exe.
I have localized this app for english, german and polish. Have fun.