Definitely!

I also use https://www.whatismybrowser.com for that kind of thing too.

But realistically speaking, ad networks are going to add this to their code to gather even more information about you.

To be honest, it would surprise me if they are not already doing this.

On a side note, when you install, launch and maximize TOR browser, you get a warning advising you not to maximize it. Web servers/attackers can use max screen size as an additional point to determine your identity.

That’s confusing. Wouldn’t it be better if everyone maximised their window? If you have a random window size you have a much higher chance of it being unique.

The default TOR viewport size isn't random. It picks a multiple of 200x100, with 1000x1000 as the maximum

I think the idea is preventing tracking a user between different Tor Browser sessions, not within the same session. When Tor Browser opens, it opens at a default size, regardless of computer. So there's no way to differentiate between different Tor Browser users who don't manually change the window size.

If your screen resolution is common, it's just a bit or two worth of information. But enough of those bits from various sources and you are unique.

> If you have a random window size you have a much higher chance of it being unique.

That's the whole point, multiple unique data points can whittle down the differences to a single user.

Maybe? Probably not that useful for most ads. Unless you’re selling phone cases, iPhone 8 and XS users are probably getting the same ads.