Finding a MIME type for a file on windows

In Windows 10, the different MIME types are stored in the registry at:

HKEY_CLASSES_ROOT\MIME\Database\Content Type

with a key for each content type (e. g. text/plain) under that key.

HKEY_CLASSES_ROOT\\.<ext>\Content Type (where "ext" is the file extension) will normally hold the MIME type.