Set it. Start it. Take your time.
Enter hours, minutes, and seconds, then start. Pause preserves the remaining duration; Resume continues it. Reset returns to the configured duration. The timer displays a visual completion message and does not play a sound.
Keep the tab open
A running timer measures remaining time against a deadline on your device clock, rather than counting browser callbacks. It catches up after a background tab is throttled, but device clock changes affect the result and a sleeping or closed browser cannot alert you. Reloading clears the timer. Do not rely on it for critical alarms.