32 to 64bit Firefox
 

I only realised today that a 64bit version of Firefox was available, so I gave it a go. It picks up all your 32bit bookmarks, passwords etc. and even restarts with the web pages you were viewing in 32bits, back on screen. You just install it then uninstall the 32bit version. It runs a touch faster too.

I use Waterfox, it has been my 1st choice browser for a long time, it is only available as 64bit. It looks and feels exactly like Firefox except faster, it installs all of your bookmarks and addons as soon as you install it.

It boasts:

Built with Clang-cl on Windows
No Adobe DRM
No Pocket
No data collection
Run every 64-Bit plugin
Run every Add-On (even unsigned ones!)
Windows XP 64-Bit Support

Many thanks. I did not know either. I had to uninstall 32 bit version via the Control Panel as I could not see how to do it via Settings.
Easy transition because as you say it takes all your bookmarks etc.