About waking at 6:30 AM
Half six is the school-run alarm. It is early enough to get children fed and out of the house and late enough to be sustainable across a term, which is a harder combination to find than it sounds.
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.