Restricting file upload types (Via OS native popups)

Hi guys,

This may not be possible using PHP; so admins please feel free to move this thread to the appropriate area.

Here’s my question.

I’ve seen on numerous occasions where the file types have been restricted within the OS native file upload popup. How is this done?
I’m not looking for responses with regards to restricting/validating filetypes after upload has taken place.

Cheers.

I’ve just tried the html attribute ‘accept’ but that seems to have some sort of adverse effect.
It causes the popups to appear really slow and the browsers to almost die.

Cheers