Online Countdown Timer
Set your time and press start. It rings the moment time is up — even in a background tab.
Why a countdown beats watching the clock
A clock says what time it is; it says nothing about how much of a fixed window is left. Cooking, workouts, study blocks and speaking slots share the same shape: a task with a hard duration where overrunning has a real cost — burnt food, a missed rep count, a talk that runs long. A countdown turns "keep an eye on the time" into "work until it rings," which is why it lives in kitchens, gyms, exam halls and behind podiums.
This page is a single-purpose countdown: one duration, one run, one alarm — not a multi-timer or an interval looper (see limitations below).
Setting a duration
- Type hours (0–23), minutes (0–59), seconds (0–59), or tap a preset (1/3/5/10/30 min).
- Press Start. Fields lock while running so a stray keystroke can't change a duration already counting down.
- Pause freezes the remaining time; Resume continues from exactly there.
- Reset clears the run and returns to your last confirmed duration.
- Your last-used h/m/s is remembered for next time — but a run in progress is not. Closing or reloading the tab mid-run drops back to idle.
How it stays correct in the background
A naive timer decrements a counter once a second with setInterval. That drifts, because browsers throttle timers in background or minimized tabs to save power — a "one second" tick can quietly become two or three seconds once a tab loses focus. Over a 25-minute run that adds up to real error.
This timer never trusts the tick count. Start computes one fixed value: end time = now + duration. Every tick just asks the clock "what time is it now?" and subtracts: remaining = end time − now. A throttled tab that fires once every few seconds still lands on the right answer the moment it fires, and a tab that slept past the end time sees a negative remainder on its next tick and rings immediately instead of catching up. Pause/Resume works the same way: pausing banks the remaining milliseconds, resuming recomputes a fresh end time from them.
Worked example 1 — the reverse-timer trick for a talk
Set the countdown for 12 − 2 = 10 minutes, not 12, and start it with your slot. When it rings, exactly 2 minutes remain — wrap up and stop. One subtraction, done before you start talking, replaces mental math while you're talking.
Worked example 2 — a Pomodoro study block
4 × 25 = 100 minutes of work, plus 3 short breaks between rounds = 3 × 5 = 15 minutes, plus one 20-minute long break after round four.
Total for one full set: 100 + 15 + 20 = 135 minutes (2 h 15 min), of which 100 minutes is focused work. Set 25:00 for each work block and 5:00 (20:00 on the fourth) for each break.
Worked example 3 — boiling an egg, adjusted for altitude
Water boils cooler as elevation rises (roughly 1 °C per ~300 m), so eggs cook slower. Around 1,500 m, add about 1 minute to each: 7:30 / 9:00 / 12:00. Drop the egg in as you start the countdown so both begin together.
Reference durations
| Duration | Common use | Why this length |
|---|---|---|
| 1 min | Rest between exercise sets | Recovers breath without losing heart-rate elevation |
| 3 min | Steeping tea, instant noodles | Matches most packaging instructions |
| 5 min | Micro-break, stretch, Pomodoro short break | Resets focus without losing momentum |
| 10 min | Reading sprint, warm-up | Long enough for real progress |
| 25 min | Pomodoro focus block | The duration the technique is built around |
| 30 min | Workout block, meeting time-box | Fits a full routine or agenda item |
Common mistakes
- Expecting sound before pressing Start. Browsers block audio until you interact with the page, so the sound engine only arms on the Start click — no separate "enable sound" step is possible.
- Closing the tab and expecting the run to resume. Only your last duration is remembered, not a run in progress. Keep the tab open and minimized instead, or install it as an app.
- Setting all three fields to zero. Start stays disabled with a short notice, by design, rather than silently doing nothing.
- Phone on silent. The hardware silent switch and system volume sit above any web page's control.
What this timer doesn't do
It runs one countdown at a time — it won't chain a work interval into a rest interval and back (a Tabata- or HIIT-style looper), so interval training means restarting the duration by hand each round. It isn't tied to wall-clock time either: it counts down a duration, it won't ring at "3:00 PM" — that needs a scheduled alarm. And like any browser timer, it's accurate to whole seconds, not milliseconds — fine for cooking or study, not competition-grade split timing.
Sources & further reading
Frequently asked questions
Is the timer accurate when the tab is in the background or minimized?
Yes. Instead of counting ticks, this countdown timer stores the exact end time when you press start and recomputes the time left from the clock on every update. Even if the browser throttles background tabs, the correct time shows the moment you return — and if the end time has already passed, the alarm rings immediately.
I can't hear the alarm — why, and how do I fix it?
Browsers only allow sound after you interact with the page, so this online timer arms the sound the moment you press Start. If you still hear nothing, check the system volume, the tab's mute setting and the silent switch on phones. If your browser doesn't support Web Audio, a notice appears and the alert stays visual only.
How do I use the 1/3/5/10/30 minute presets for cooking, studying or workouts?
One tap sets a common time: 3 minutes for instant noodles or tea as a cooking timer, a 5 minute timer for breaks and stretching, 10 minutes for a short study sprint, 30 minutes for a focus session or workout. After a preset just press Start — your last setting is restored on your next visit.
What's the difference between a stopwatch and a countdown timer?
A stopwatch counts up from zero to measure how long something takes. A countdown timer does the opposite: you set a duration, it counts down to zero and then rings. Use a stopwatch to record times, and a timer with alarm to be reminded.
Does it keep working if the internet disconnects?
Yes. Once the page is loaded, everything runs inside your browser and nothing is sent to a server. A running online timer keeps counting down and rings even while offline, and you can install it as a PWA for offline use.