Chronometer

What is Chronometer?

Chronometer provides a high-precision stopwatch and countdown timer with lap recording, split time tracking, and millisecond accuracy. It uses the Performance API (performance.now()) for timing resolution better than 1 millisecond, avoiding the drift issues of setInterval-based timers. The tool supports multiple concurrent timers, lap comparison with average and best-lap indicators, and exports timing data as CSV for analysis.

UX researchers timing task completion, athletes tracking interval training, and developers measuring workflow durations during productivity analysis. The tool runs entirely in your browser — your data never leaves your device.

How to Use Chronometer

1. Click Start to begin the stopwatch, or enter a duration and click Start for countdown mode
2. Use the Lap button to record split times without stopping the main timer
3. Pause and resume as needed — the timer compensates for browser tab suspension
4. Export lap data as CSV or copy the full timing summary for your records

Common Use Cases

• Timing code execution intervals during manual performance profiling sessions
• Recording lap times for athletic training with split comparisons
• Measuring task completion times during usability testing sessions
• Running countdown timers for presentation segments or meeting time-boxing

Pro Tips

• Browser tabs in the background throttle JavaScript timers to once per second — the tool uses timestamps rather than intervals so accumulated time stays accurate even after tab-switching
• For precise benchmarking of code, use the browser's built-in Performance API or console.time() instead — this tool is better for human-scale timing tasks
• The lap comparison feature highlights your fastest lap in green and slowest in red, so you can immediately spot consistency patterns in repetitive tasks

Why Use This Tool?

• Privacy-first: All processing happens locally in your browser. No data is transmitted to any server.
• No installation required: Works in any modern browser on desktop or mobile.
• Completely free: No account, no credit card, no usage caps.
• Fast and reliable: Powered by modern Web APIs for near-instant results.

Related Concepts

Learn more about related topics: Performance API, Lap timer, Time tracking, Precision timing.

Frequently Asked Questions