Stopwatch & Timer

When to use Stopwatch & Timer

You're doing interval training — 40 seconds on, 20 seconds rest — and your phone keeps pulling you into notifications every time you unlock it to check the split. Open this page in a dedicated browser tab: set the countdown timer to 40 seconds, start it, and step away. When it hits zero the Web Audio API plays an alarm and a browser notification fires (if you've granted permission), so you hear it even when the tab is in the background. Switch to stopwatch mode for lap-based timing: track swim lengths, cooking steps, or how long a client call actually ran. The timer uses timestamps rather than intervals, so it stays accurate even when the tab isn't active. Nothing is logged — close the tab and the session is gone.

• Time 40-second intervals during a HIIT workout
• Track lap splits for a swim set without touching your phone
• Measure how long a client call actually ran for billing records

About this tool

Most stopwatch apps live on your phone and keep disappearing behind notifications. This one stays in your browser tab — start, lap, stop, reset, and back again. Precision timing uses requestAnimationFrame so splits are accurate enough for interval training, cooking timers, timed study blocks, or tracking how long a client call actually ran. Countdown timer mode plays an alarm when it hits zero, so you can set it and step away. Two tools in one tab, no download, no app store — just open and start timing.