Countdown timer
Simple online countdown timer with full-screen mode and a sound at zero. Set hours, minutes and seconds, or tap a preset. Works offline.
Runs on your device. Nothing is sent to a server. Keeps time even if the tab is in the background; a sound plays at zero.
How it works
Set a time or tap a preset like 5 min, then press Start. The remaining time also shows in the browser tab title so you can switch tabs. Full screen is handy for classrooms and presentations.
The timer uses the clock, not a counter, so it stays accurate even when the browser slows background tabs. A short beep plays when it reaches zero; keep the tab open and the device unmuted.
Questions
Will the alarm sound if my phone is locked?
Usually not. Mobile browsers pause audio on locked screens. Keep the screen on, or use full screen mode.
Can I run several timers?
Open the page in two tabs. Each runs on its own.