Online Stopwatch
High-precision stopwatch with millisecond accuracy, lap recording, and keyboard shortcuts
How to Use the Online Stopwatch
1. Start Timing
Click the Start button or press Space to begin. The stopwatch counts up with millisecond precision using your device's high-resolution clock.
2. Record Laps
Click Lap or press L to record split times without stopping. Each lap shows both the interval time and total elapsed time.
3. Export Data
Click Export CSV to download your timing data. The file includes all lap times and splits, ready for spreadsheets or analysis.
Common Uses for a Stopwatch
Sports & Fitness
Track running laps, swimming splits, interval training, and workout durations with precision timing. Record personal bests and compare performance over time.
Productivity & Study
Time focused work sessions, Pomodoro intervals, study blocks, and presentations. Use lap timing to track individual tasks within a larger session.
Cooking & Kitchen
Time cooking steps, boiling, steeping, and marinating. The stopwatch runs in the background so you can switch tabs while timing.
Science & Testing
Time experiments, reactions, and test procedures. Export CSV data for accurate record-keeping and further analysis in spreadsheets.
Understanding Stopwatch Precision
A stopwatch is a timing instrument used to measure elapsed time. Traditional mechanical stopwatches rely on spring-driven mechanisms and are typically accurate to about 1/5 of a second. Digital stopwatches improved this to 1/100 of a second. Our online stopwatch goes further, using the browser's performance.now() API to achieve sub-millisecond precision — far exceeding what most physical stopwatches can offer.
The performance.now() method returns a high-resolution timestamp measured in milliseconds, accurate to 5 microseconds in most browsers. Unlike Date.now(), which is subject to system clock adjustments and can jump forward or backward, performance.now() uses a monotonic clock that always moves forward at a constant rate. This makes it ideal for measuring precise time intervals.
Stopwatch vs. Timer: What's the Difference?
While both are timing tools, a stopwatch and a timer serve opposite purposes. A stopwatch counts up from zero, measuring how long an event takes. A timer (or countdown timer) counts down from a preset duration and alerts you when time is up. Use a stopwatch when you want to measure duration, and a countdown timer when you know in advance how long you want to wait.
Lap Timing Explained
Lap timing lets you record split times without stopping the main clock. Each lap shows two values: the interval time (how long that specific lap took) and the split time (total elapsed time). The fastest lap is highlighted in green and the slowest in red, making it easy to identify performance variations. This is invaluable for athletes tracking split times during training, coaches analyzing performance, or anyone measuring repetitive tasks.
Keyboard Shortcuts for Power Users
Our stopwatch supports full keyboard control for hands-free operation. Press Space to start or pause the timer, L to record a lap, R to reset everything, and F to enter fullscreen mode. This makes the stopwatch ideal for situations where you need to keep your eyes on what you're timing rather than looking at the screen to click buttons.
Frequently Asked Questions
How accurate is this online stopwatch?
This stopwatch uses the high-resolution performance.now() API providing sub-millisecond precision. The display updates every 10ms for smooth visual feedback. Accuracy depends on your device's clock, which is typically synced via NTP.
What keyboard shortcuts are available?
Press Space to start/stop, L to record a lap, R to reset, and F to toggle fullscreen. These shortcuts allow completely hands-free operation.
Can I export my stopwatch data?
Yes. Click the Export CSV button to download your elapsed time and all lap data as a CSV file. The file can be opened in Excel, Google Sheets, or any spreadsheet application.
Does the stopwatch work offline?
Yes. Once the page is loaded, the stopwatch works entirely offline using your device's internal clock. No internet connection is needed to continue timing.
What is the difference between a stopwatch and a timer?
A stopwatch counts up from zero to measure elapsed time, while a timer counts down from a set duration and alerts you when it reaches zero. Use a stopwatch when you want to measure how long something takes, and a timer when you know in advance how long you want to wait.
Does the stopwatch work on mobile devices?
Yes. The stopwatch is fully responsive and works on any modern mobile browser including Safari on iOS and Chrome on Android. All features including lap recording and CSV export work on mobile.