> Tor Browser in its default mode is starting with a content window rounded to a multiple of 200px x 100px to prevent fingerprinting the screen dimensions. The strategy here is to put all users in a couple of buckets to make it harder to single them out. That worked so far until users started to resize their windows (e.g. by maximizing them or going into fullscreen mode). Tor Browser 9 ships with a fingerprinting defense for those scenarios as well, which is called Letterboxing, a technique developed by Mozilla and presented earlier this year. It works by adding white margins to a browser window so that the window is as close as possible to the desired size while users are still in a couple of screen size buckets that prevent singling them out with the help of screen dimensions.

Is it possible to disable, or make the page render bigger behind the scenes but scale to display, or anything to stop the massive letterboxing I seem stuck with on a very normal resolution laptop?

I wish the letterboxing margins could be set to a color, in my case black. I've installed the Dark Reader extension but when I enable it the margins are still the default white color.

What do you mean by this?