The problem with browser timers is not accuracy, it is walking away. Set one, switch to another tab to work, and the browser throttles that tab’s clock — to once a second, and after five minutes to once a minute — so the alarm arrives late. This page sidesteps that by handing the alarm to the audio clock the instant you press start. Browsers throttle the screen timer; they do not throttle sound that is already scheduled. A countdown, an interval timer for training, and a stopwatch with laps all live here.
Yes, and this is the part most web timers get wrong. Chrome and the other browsers slow background timers to once a second, then to once a minute after five minutes, which is why a page relying only on a JavaScript interval can be a full minute late. This one schedules the finishing sound on the Web Audio clock when you press start, and audio scheduling is exempt from that throttling. The on-screen digits may stall while the tab is hidden; the sound will not. In interval mode, every round transition is scheduled up front the same way.
Raise the slider next to the speaker icon — the real alarm sounds each time you let go, so you can compare on the spot. If that is not enough, check the device volume: browser audio cannot exceed it, so a page at full volume on a device at 20% is still capped at 20%. The alarm is a square wave alternating between 2,600 Hz and 1,950 Hz. That is the 2–4 kHz band human hearing is most sensitive to, and a square wave carries enough harmonics that background noise masking one frequency cannot hide the rest. It is the same reason alarm clocks buzz rather than chime.
Three things to check. The speaker icon may be off — turning it on plays a tone immediately, so you will know at once. Browsers also block audio until the visitor has interacted with the page; pressing start counts, so a timer you set up but never started will be silent. And on iOS, Safari respects the physical mute switch for web audio, so check the side of the device.
Two ways. The quick one: on the timer tab press the 25 chip and turn on Repeat, and it will chime every 25 minutes and keep going. The complete one: on the interval tab press the "Study 25/5 × 4" chip, which runs four blocks of 25 minutes of focus and 5 minutes of rest, sounding a short tone and changing colour at every boundary.
Because a session of eight rounds is eight work intervals and the seven rests between them. Adding a rest after the final round would leave you waiting ten seconds after the workout is already over, and would overstate the total time. The session ends the moment the last work interval does.
The lap is the time since the previous lap; the fainter number beside it is the elapsed time from the start. Running four laps of a track, the split is what each lap took and the total is your time as you crossed each line. Copy takes both, tab-separated, so it pastes straight into a spreadsheet.
The display is recalculated from the device clock every tick, so error cannot accumulate. The sound rides on the audio hardware clock, which is if anything more precise than the screen. The one case no web timer can cover is a laptop suspending, which stops the CPU and the audio together: on waking, the remaining time is correct again, but an alarm whose moment passed while the machine slept does not come back.