Chrome/Firefox: There are plenty of reasons you might not want to give out your real email address when signing up for a site or service. Maybe you're really big on privacy; or, more likely, you just hate spam, and figure the fewer places that know your real email address, the better.
Browser cookies are useful in some instances; unpleasant in others. While they can save you from having to go through a complicated authentication process whenever you're trying to access your favourite sites, they can also store data on what you've done on a particular website -- which can then be used to serve you more "relevant" advertising at a future point.
I recently stumbled across the extension Toby (Chrome, Firefox), and I'm surprised at how much I love it. So much so that it has replaced the pretty Chrome Delight and Earth View from Google Earth extensions I've been using whenever I open a new tab. I'm one-hundred per cent Toby now, because it's one of the best ways I've seen to get a little more control over all those open tabs in my browser.
Chrome/Firefox: If you've used a web browser at any point in the past eight years, you've surely heard of the extension Turn Off the Lights (Chrome, Firefox). It's the best way to automatically embiggen your YouTube videos when you start watching and, of course, dim your browser's background for a prettier view (even if you're already using YouTube's dark mode).
