Can multiple associations to a single file type be set/initialised in strictly administrative install mode?

[Frank James]

I'd like to set a list of applications to 'Open with' in administrative install mode.

An installer installs a number of applications. Some of the applications are to be associated with a single file type, so that right-clicking on a file and selecting 'Open with' lists the applications. This can be done for a user by setting appropriate values for the following key

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.ext\OpenWithList

However, there doesn't appear to be an equivalent key in HKEY_LOCAL_MACHINE. I understand that Microsoft wants the user to set their own file associations but if the user doesn't know which applications can be used to open the file type it would useful to provide a list at the All Users level. Is it possible?

[Gavin Lambert]

On Wednesday, July 15, 2026 at 1:09:53 AM UTC+12 Frank James wrote:

An installer installs a number of applications. Some of the applications are to be associated with a single file type, so that right-clicking on a file and selecting 'Open with' lists the applications. This can be done for a user by setting appropriate values for the following key

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.ext\OpenWithList

However, there doesn't appear to be an equivalent key in HKEY_LOCAL_MACHINE. I understand that Microsoft wants the user to set their own file associations but if the user doesn't know which applications can be used to open the file type it would useful to provide a list at the All Users level. Is it possible?

That's the wrong path to make file association registrations in an installer.  See https://jrsoftware.org/isfaq.php#assoc

The preferred method is to register OpenWithProgids; the OpenWithList is a legacy fallback.