Internet Explorer 10 in Windows 8 and Windows RT contains an embedded version of Flash, updated through Windows Update. However, not all Flash sites can actually use this embedded Flash. On Windows 8, the Metro version of Internet Explorer can only use Flash on a list of sites that Microsoft authorizes. Only the desktop version has full unfettered Flash access. On Windows RT, both Metro and desktop Internet Explorer use the whitelist.

That’s going to change tomorrow when the list will change from a whitelist to a blacklist. Flash will work on every site except a selection that Microsoft is explicitly blocking due to known incompatibilities with touch. Desktop Internet Explorer 10 on Windows 8 will continue to be unrestricted.

Why the about turn? Microsoft says that most sites with Flash content do in fact work sufficiently well with touch, enough so that a blacklist approach provides a better user experience. Fewer than four percent of sites that the company tested didn’t work properly, and most of those non-functional sites didn’t work because they also needed other browser plugins.