About waking at 4:00 AM
Four in the morning is a shift-work and long-haul-travel hour. Waking here reliably means going to bed before nine, which is the part most people skip — and the reason a 4 a.m. alarm so often produces a week of sleep debt rather than a productive routine.
Leave the tab open
A browser alarm can only ring while its page is open. It does not have to be the tab you are looking at, and on a desktop it does not have to be the window in front — but closing the tab or quitting the browser stops it. For anything you genuinely cannot miss, set a second alarm on your phone as a backup. That is true of every browser-based alarm clock, not just this one.