Does your interval timer beep on time with the screen off?
It is the most common way timer apps fail, and the hardest to see. We recorded every beep to find out.
By Springlab · 17 October 2026. We make Interval Timer. This page shows how we tested it, what we found, and what we have not tested yet.
What goes wrong
We read 2,495 reviews of 1 to 3 stars for the five most-installed interval timer apps on Google Play. The top complaints were about timing, not features:
| Complaint | Reviews |
|---|---|
| Stops, pauses or freezes in the middle of a workout | 397 |
| Fights with music, headphones or the volume | 258 |
| No sound with the screen off or in another app | 248 |
| Beeps late or skipped | 51 |
Counts are keyword matches, checked by reading samples. The cause is usually the same: Android saves battery by putting a phone with its screen off into a deep sleep (Doze), and some phone makers add their own, stricter battery savers. A timer that counts on the screen's clock stops when the screen does.
How we measured
- We recorded the app's own audio output from the phone's mixer, with a time stamp on every block of sound.
- We found each beep in the recording and compared it with the exact time it should play, rebuilt from the workout settings, not read from the app.
- We calibrated the recording path with a test click once a second: it reads a steady 32 ms late, which we take off.
- The phone: a Galaxy S23 on Android 15, with the release build installed as a user would, and no battery-saver exemption.
Results
| Test | Beeps heard | Error vs ideal | Gap evenness (p95 / worst) | Drift |
|---|---|---|---|---|
| Tabata, screen on | 65 of 65 | about −5 ms | 1 ms / 3 ms | +0.09 ms per min |
| 30 minutes, screen off, phone forced into deep sleep | 241 of 241 | about +3 ms | 1 ms / 11 ms | −0.01 ms per min |
For scale, people start to notice a beat that is off by about 20 to 30 ms. Before we rebuilt the sound engine, an early version of our own app missed 2 of 65 beeps and was up to 329 ms late, with gaps uneven by 170 ms. The fix was to place each beep at an exact sample in one audio stream, timed from the audio hardware's clock, not from a screen timer.
What we have not tested yet
- Cheap phones and phone makers with strict battery savers (Xiaomi, some Samsung A-series settings).
- Bluetooth headphones, which add their own delay of 100 ms or more.
- A whole night with the phone on a desk, without forcing the deep sleep.
We will add these results here when we have them.
Test your own timer
- Start a Tabata (20/10 × 8) on the timer you use, and lock the screen.
- Record it with a second phone's voice recorder, close to the speaker.
- Look at the recording's waveform: every beep should be there, and the gaps between them should look the same.
And a note on browser timers, including ours: a web page cannot run as a service, so most phones pause it when the screen locks. Keep the screen on, or use an app.
Questions
Why does my interval timer stop with the screen off?
Android puts a phone with its screen off into a deep sleep to save battery, and some makers add stricter savers. A timer that is not built as a foreground service, or counts on a screen timer, stops or drifts.
Do browser interval timers work with the screen locked?
Usually not. Phones pause background tabs. Keep the screen on, or use an app that runs as a service.
How accurate is the Interval Timer app?
On a Galaxy S23, every beep of a 30-minute screen-off workout played, within about 3 ms of the ideal time, and the gaps between beeps were never more than 11 ms off.