Does the 20 second timer work accurately in background tabs?

Yes. TimerBox uses millisecond-accurate timestamp offsets via Date.now(), so your 20 second countdown never loses a tick if you switch applications or tabs.

Will an audible chime sound when the 20 seconds finish?

Yes. As soon as the timer reaches zero, an audible chime synthesized via the Web Audio API will play.

Can I expand this 20 second timer to fullscreen?

Yes. Tap the fullscreen button or press "F" on your keyboard to view giant countdown digits across your screen.

Is this second timer completely free with no account?

Yes. TimerBox is 100% free with no sign-up, no downloads, and no ads.

20 Second Timer

00:20

Free Online 20 Second Timer Countdown

•Free 20 Second Timer•20s Countdown with Alarm•Background Tab Accuracy•Instant Millisecond Clock

Accurate 20 Second Countdown Timer

Need a fast 20 second timer for high-intensity intervals, kitchen steeping, classroom games, or quick reaction drills? TimerBox provides an instant countdown with audible chime alerts and fullscreen mode that begins the exact millisecond you click Start or press spacebar.

Running locally in your browser with Date.now() timestamp calculations, this timer guarantees zero drift and background tab precision across desktop, tablet, and mobile.

Other Instant Timers

1 – 10 Minutes

1 Minute Timer
2 Minute Timer
3 Minute Timer
4 Minute Timer
5 Minute Timer
6 Minute Timer
7 Minute Timer
8 Minute Timer
9 Minute Timer
10 Minute Timer

11 – 20 Minutes

11 Minute Timer
12 Minute Timer
13 Minute Timer
14 Minute Timer
15 Minute Timer
16 Minute Timer
18 Minute Timer
20 Minute Timer

21 – 40 Minutes

21 Minute Timer
22 Minute Timer
25 Minute Timer
28 Minute Timer
30 Minute Timer
35 Minute Timer
40 Minute Timer

45 – 120 Minutes

All Timers Directory
45 Minute Timer
50 Minute Timer
55 Minute Timer
60 Minute Timer
90 Minute Timer
2 Hour Timer

Start Your 20 Second Countdown Now

No accounts. No sign-up. Just hit Start or tap your spacebar to begin counting down.