FType

ftype is a command-line utility in Windows that displays and modifies the mapping between file types (ProgIDs) and the commands used to open files of those types. It operates with the file type associations stored in the system registry, linking a ProgID to the program or command that should run when a file of that type is opened.

ftype works in conjunction with the assoc command. While assoc maps a file extension to a file type (ProgID), ftype maps that ProgID to the actual open command. This separation allows users to adjust how files are opened without changing the extension-to-type mapping. Modifying these associations affects how Windows launches applications for double-clicked files or for shell open actions.

Usage and examples:

- Display all registered file types and their commands: ftype

- Show the command for a specific type: ftype txtfile

- Define or change the open command for a type: ftype txtfile="C:\Windows\System32\notepad.exe" "%1"

- The %1 placeholder represents the file being opened.

Notes:

- Writing to the file type mappings typically requires appropriate system privileges, as the changes affect the registry under HKEY_CLASSES_ROOT.

- On modern Windows versions, some associations may be governed by per-user settings or system policies, which can override or supplement the traditional registry-based approach.

See also:

assoc, ProgID, HKEY_CLASSES_ROOT, open command.