WebKit maps accept extensions to MIME types, drops the ones it doesn't know, and then limits the Files app to whatever is left. For a mail archive tool, that is almost everything that matters.

I run a browser tool that opens Outlook .pst and .ost files without Outlook. For months the homepage said it worked on a Mac, a PC, a Chromebook, or an Android phone. Google was suggesting "open pst file on ipad" next to "on android" and "on chromebook". Bing showed tablet-flavoured queries. The site said nothing about an iPad or an iPhone.

That gap was not just marketing. On iOS the file picker itself can quietly refuse the files the page is built for. Here is what I measured, why the picker behaves that way, and what the page now does about it.

First, does the engine even open a PST?

Before writing any "works on iPad" claim, I ran the live site in Playwright's WebKit 26.6 with the iPad Pro 11 and iPhone 15 profiles.…