How accurate is this online stopwatch?

The stopwatch measures elapsed time using performance.now(), which provides microsecond-level clock resolution in standard modern browsers.

Can I record dozens of laps in one trial?

Yes. You can record dozens of laps in a single session; all records are held temporarily in local component memory.

Does the stopwatch continue running if I switch tabs?

Yes. When you return to the tab, the display computes elapsed time directly from the start timestamp, keeping time accurate.

Free & Private Online Browser Utility

Online Stopwatch with Split Lap Times Free

Measure elapsed time with millisecond precision directly in your browser. The stopwatch records lap intervals, calculates split differences, and displays running hours, minutes, seconds, and centiseconds. All timing computations use the browser performance API to accurately record interval measurements without network latency or external tracking.

How to use

Step 1: Start the Stopwatch

Click Start to begin timing. The display tracks elapsed centiseconds and seconds in real time.
Step 2: Record Lap Splits

Click Lap while running to stamp intermediate interval markers in the chronological lap table.
Step 3: Stop and Export

Click Stop to freeze the counter. You can copy the lap breakdown or click Reset to return to zero.

Options explained

Lap Recording

Captures the split duration and cumulative elapsed time without interrupting the active clock.

When to use: Use during athletic training, sprint tests, or multi-step benchmarking.

Centisecond Precision

Displays hundredths of a second alongside standard minute and second counters.

When to use: Use when fine-grained timing precision is required.

Clear & Reset

Wipes recorded lap rows and resets clock counters to 00:00:00.00.

When to use: Use when preparing to record a new, distinct timing trial.

Worked example

Input: Single trial with 3 recorded laps over a 45-second duration

Output: Lap 1: 00:14.20 | Lap 2: 00:15.10 | Lap 3: 00:15.70 | Total: 00:45.00

Calculated via delta timestamps derived from window.performance.now().

Tips & limits

Lap rows calculate both individual interval durations and total cumulative elapsed time.
The monospace tabular number layout avoids visual jitter as fractions of a second tick by.
Performance.now() provides sub-millisecond precision unaffected by system wall-clock adjustments.

Common problems

Laps cleared accidentally after stopping: Reset wipes the lap history table; make sure to copy your desired lap numbers before clicking Reset.
Timing appears delayed on low-power devices: Ensure background battery-saver modes are disabled so the browser maintains consistent refresh rates.

Frequently Asked Questions (FAQ)

How accurate is this online stopwatch?: The stopwatch measures elapsed time using performance.now(), which provides microsecond-level clock resolution in standard modern browsers.
Can I record dozens of laps in one trial?: Yes. You can record dozens of laps in a single session; all records are held temporarily in local component memory.
Does the stopwatch continue running if I switch tabs?: Yes. When you return to the tab, the display computes elapsed time directly from the start timestamp, keeping time accurate.

How to use

Step 1: Start the Stopwatch

Step 2: Record Lap Splits

Step 3: Stop and Export