Search notes:

Registry: HKEY_CLASSES_ROOT\SystemFileAssociations

The registry key HKEY_CLASSES_ROOT\SystemFileAssociations guarantees that Shell extensions are installed regardless of the current default ProgID or user customization and define fallback attributes for file types and enable shared file associations.
Subkeys allow to define behavior of attributes and enable shared file associations for file types.

Registry keys for perceived types

HKEY_CLASSES_ROOT\SystemFileAssociations also contains the keys for perceived types such as
A perceived type differs from a specific type in that the perceived type refers to a category of file format types.

See also

HKEY_CLASSES_ROOT\.ext

Index