How to use the stopwatch?

Click 'Start' to begin timing. Use the 'Lap' button to record intermediate times. You can pause, resume, or reset the timer at any time.

Is it accurate to milliseconds?

Yes, our stopwatch uses high-resolution browser timers to provide accuracy up to 1/1000th of a second.

Sport Tool

Online Stopwatch

High-precision stopwatch with lap times. Perfect for interval training, study tracking, and speed tests. Accurate to the millisecond.

00:00:00 .000

Laps & Splits

Shortcuts: [Space] Start/Stop · [L] Lap · [R] Reset

What is an Online Stopwatch?

An online stopwatch is a digital timepiece that counts upwards from zero, specifically designed to measure the amount of time that elapses between its activation and deactivation. Unlike a simple countdown timer, it allows for "Laps"—recorded splits that show intermediate times during a larger session.

The Advantage of Millisecond Precision

Standard web clocks often update only once per second. Our Online Stopwatch utilizes high-resolution browser timers (`performance.now()`) to ensure accuracy up to the thousandth of a second (1ms). This level of precision is essential for competitive gaming speedruns, scientific laboratory experiments, and professional athletic training.

How to Use Lap Timing

Lapping is a powerful feature that lets you mark intervals without stopping the main clock. For example, if you are running 400m intervals, you can click "Lap" as you cross each 100m mark. The tool will calculate the exact time spent on that specific lap and your cumulative total time.

Best/Worst Highlighting: Our tool automatically scans your recorded laps to find your fastest (Green) and slowest (Red) splits, giving you instant performance feedback.
Session Persistence: Your current stopwatch session is saved locally. If you accidentally refresh the page, your time and laps will remain exactly where you left them.

Frequently Asked Questions

Q: Is it accurate enough for racing?

While extremely precise for a web application, critical competitive racing should use hardware-based timing systems that account for finger-to-screen latency.

Q: Can I export my data?

Yes, once you record one or more laps, a "Download CSV" button will appear. This creates a spreadsheet-ready file of all your recorded times.

Q: Does it work while my screen is locked?

Modern mobile browsers power-throttle background tabs. We use a "Visible Wake Lock" strategy where possible, but for large sessions, it is best to keep the tab visible.