Time Tools

Stopwatch & Timer

A precise stopwatch with millisecond accuracy and lap timing, plus a countdown timer with visual alarm.

00:00:00.000
Space to start/pause   L for lap   R for reset
Laps
No laps recorded.

How to use this tool

  1. Pick a mode with the Stopwatch and Countdown tabs at the top.
  2. For the stopwatch, press Start (or Space) to begin, then Lap (or L) to capture the current time as a lap.
  3. For the countdown, set the hours, minutes, and seconds in the H, M, and S fields, then press Start (or Space).
  4. Pause and resume with Pause / Resume (or Space), and clear back to zero with Reset (or R).
  5. Read the large display in HH:MM:SS.mmm format — it tracks down to the millisecond.
  6. When the countdown reaches zero, the display flashes red and a short alarm tone plays.

Why this tool is helpful

Measure code & build times

Millisecond resolution makes it easy to time how long a script, build, or CI step takes without leaving your workflow.

Compare repeated runs

Lap captures each attempt, and the fastest lap is highlighted green while the slowest is red — so outliers in a benchmark stand out.

Run focused sprints

The countdown is ideal for Pomodoro sessions, standups, lightning talks, or any timeboxed task, with an audible alarm when time's up.

Stay on the keyboard

Space, L, and R control start/pause, lap, and reset, so you can time things without reaching for the mouse.

Readable to the millisecond

The HH:MM:SS.mmm format matches the resolution timing tools and profilers report, making cross-checks easy.

Private by design

Everything runs in your browser. No data leaves your machine, and it keeps working offline.

FAQ

What's the difference between the stopwatch and the countdown?

The stopwatch counts up from zero and lets you record laps. The countdown counts down from a time you set and fires an alarm at zero.

How accurate is the timing?

Elapsed time is computed from wall-clock timestamps with the display updated via requestAnimationFrame, giving a countdown precision of roughly ±16ms. That's ideal for human-scale timing, but it isn't meant for sub-millisecond microbenchmarks.

Why don't the keyboard shortcuts work while I'm typing?

Shortcuts are deliberately disabled when focus is inside an input field, so entering countdown values doesn't accidentally start, lap, or reset the timer.

Do laps show split time or total time?

Each lap records the total elapsed time since the stopwatch started at the moment you press Lap, not the delta since the previous lap. The green/red highlight compares those totals.

What happens if I switch tabs while it's running?

Because timing is based on timestamps rather than incrementing a counter, elapsed time stays correct even in the background. The display simply catches up when you return.

Is there a limit on countdown values?

Hours are capped at 99 and minutes and seconds at 59, matching the conventional hh:mm:ss range.

Does anything get sent to a server?

No. The timer, laps, and alarm all run locally in your browser, so nothing you time is uploaded or logged.