How Does the Alarm Work?
Alarms you add are stored in your browser's local storage and stay in the list even after you close and reopen the page. When an alarm's time arrives, you'll get a sound alert and an on-screen banner as long as this tab is open. After it rings and you dismiss it, the alarm turns itself off automatically; toggle it back on to reuse it.
Notifications
If you'd also like to be notified while the tab is in the background, click "Enable desktop notifications" and grant permission. Without permission, the alarm still rings with sound as long as the tab is visible.