I'm using Firefox, and current on updates.Usually this is where you might get the obligatory "use the search function" spiel, but it is actually a little tricky to find this post if you don't have an idea of what terms to look for.
Simply put, though, just press F12 and run either code in the console. The exact steps to actually run the code will vary a bit by browser, but F12 is pretty standard for getting you to the right place.