Windows Explorer is slow because of icon lookup

Hi Paul,

In the most recent Windows Weekly, you mentioned Windows 11 Explorer slowness when sorting files by extension type. I believe this has always been the case.

When Explorer populates a folder view using the Win32 listview common control it needs to attach an icon image. This is typically done via (I believe) a registry lookup so that the file association is matched to the application that would normally ‘open’ that file, e.g. somefile.sln will show a tiny Visual Studio icon alongside. This lookup is very slow and it’s one of the reasons why Explorer does not (or at least did not previously) populate all the files into the listview when there are lost of files within a given folder. The knock-on effect of this behaviour is that Explorer can’t do ‘Select by *.ext’ type operations as the the listview doesn’t contain all the files to select from.

You can see this behaviour for yourself. Navigate to a folder that contains lots of files; then press ‘page down’. The delay in populating the next screen of content is often easily visible.

Leonard