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Online 12 hours countdown timer. Starts automatically with 15 alarm sounds to choose from. Fullscreen mode for classrooms and big screens.
This 12 hours countdown timer starts automatically. When the time is up, you'll hear an alarm sound. Keep this browser tab open and your volume turned up.
A 12-hour timer represents half a day. It's used for extended fermentation processes, overnight timing, long-duration cooking, and as a reminder for tasks 12 hours away.
A 12 hours timer is great for long study sessions, slow cooking, marathon gaming, or extended work sprints. Choose from 15 alarm sounds including loud fire alarms and sirens, adjust how long the alarm rings, and customize the display with 60+ fonts and multiple color themes. Hit fullscreen to use it on a big screen, projector, or classroom TV.
The timer starts counting down as soon as this page loads. When it reaches zero, your selected alarm sound plays. You can pause, resume, or reset the timer at any time using the controls. To change the alarm sound, click the sound icon and choose from options like Classic Bell, Fire Alarm, Radar Ping, Rooster, and more. Adjust the ring duration from 30 seconds up to 10 minutes depending on how loud and long you need it.
Extended timers like 12 hours are designed for long-running processes where you need a reliable notification when time's up. Set it and forget it — the alarm will sound even if this tab is in the background. Perfect for slow-cooking, fermentation, overnight processes, and any task that needs a reliable endpoint reminder.
No app or download needed — works instantly in any modern browser on phones, tablets, laptops, and desktops. Bookmark this page to quickly return to your 12 hours timer anytime. You can also share this timer with others using the share button — they'll get the exact same timer with your settings.
Need a different kind of timer? Try the Pomodoro Timer for structured work sessions with automatic breaks, the Interval Timer for HIIT and circuit training, or the Classroom Timer for visual countdowns with fun animations. For tracking multiple things at once, use Multiple Timers.