The Online Stopwatch times an activity to the nearest hundredth of a second, with start, stop, and reset controls plus lap tracking for recording multiple splits within a single run. Elapsed time is derived from a stored start timestamp rather than an accumulating counter, which keeps the displayed time accurate even if the browser tab is backgrounded during a long run.
Start, stop and reset the stopwatch
Starting the stopwatch records the current timestamp and begins displaying elapsed time immediately, updating continuously to hundredths of a second. Stopping pauses the display and records the accumulated paused duration, so a resumed run continues from where it left off rather than restarting the elapsed count. Resetting clears the elapsed time and any recorded laps back to zero.
The Online Stopwatch recalculates elapsed time from the stored start timestamp on every screen update rather than incrementing a running counter, which is what keeps the display correct after the tab has been minimized or the device has gone to sleep briefly during a long timed activity.
Record and compare lap times
Pressing the lap control while the stopwatch is running records the current elapsed time as a lap without stopping the main timer, useful for tracking multiple segments of a single continuous activity such as a multi-lap run or a repeated task. The Online Stopwatch lists each lap with both its total elapsed time and its delta from the previous lap.
The fastest and slowest laps in the list are highlighted automatically once at least two laps are recorded, making it easy to spot which segment of a run was quickest or slowest without scanning every value manually. A lap delta of 1:12.45 shown against a previous lap of 1:15.30 immediately shows an 2.85-second improvement without needing separate subtraction.
Use keyboard shortcuts
Three keyboard shortcuts control the stopwatch without needing the mouse: the space bar starts and stops the timer, the L key records a lap, and the R key resets the stopwatch to zero.
This set of shortcuts supports one-handed operation, useful when the other hand is occupied holding a device, a piece of equipment, or a stopwatch mount during the activity being timed.
Keyboard control also reduces the delay between deciding to start or stop and the action actually registering, since a keyboard press avoids the extra step of visually locating and clicking an on-screen button.
Export lap times
A completed set of laps can be exported as a CSV file or copied directly to the clipboard, useful for building a training log across multiple sessions or importing timing data into a spreadsheet for further analysis.
The Online Stopwatch includes both the elapsed time and the delta for each lap in the exported data, matching what is shown on screen.
Keeping an exported record across sessions makes it possible to track improvement over time in a way that a single browser session cannot, since closing the tab clears the stopwatch's live state entirely.
Understand timer accuracy
Displayed precision is limited to hundredths of a second, a deliberate choice rather than a technical shortfall, since most modern browsers deliberately coarsen their internal timer resolution as a security measure against timing-based side-channel attacks. Claiming millisecond precision on top of a coarsened browser timer would be a false claim the display cannot actually back up.
The Online Stopwatch uses requestAnimationFrame to drive its display updates rather than a fixed-interval timer, which synchronizes the visual refresh with the browser's own rendering cycle and avoids the small drift that a setInterval-based timer accumulates over a long-running session.
Frequently asked questions
How accurate is the online stopwatch?
The stopwatch displays elapsed time to the nearest hundredth of a second. This limit reflects the timer resolution modern browsers deliberately provide, rather than a shortfall in the calculator; claiming finer precision than the browser can reliably deliver would not be accurate.
Does the stopwatch keep running if I switch to another tab?
Yes. Elapsed time is calculated from a stored start timestamp each time the display updates, not from an incrementing counter, so switching tabs or briefly locking the device does not cause the displayed time to drift or fall behind.
How do I record a lap time without stopping the stopwatch?
Press the lap control, or the L key, while the stopwatch is running. The current elapsed time is added to the lap list immediately, and the main timer continues running without interruption.
What do the keyboard shortcuts do?
The space bar starts and stops the stopwatch, the L key records a lap, and the R key resets everything to zero. All three work without needing to click an on-screen button, supporting one-handed operation.
Can I export my lap times?
Yes. Lap times can be exported as a CSV file or copied to the clipboard directly, including both the elapsed time and the delta for each lap, useful for building a training log across multiple sessions.
How does the stopwatch highlight the fastest and slowest laps?
Once at least two laps are recorded, the shortest and longest lap durations in the list are marked automatically, making it easy to identify the best and worst segments of a run without comparing every value by hand.
Why does the stopwatch not show milliseconds?
Browsers intentionally reduce timer precision below the millisecond level to prevent certain security exploits. Displaying hundredths of a second matches the precision the browser can reliably provide, rather than showing a level of detail that would not be trustworthy.
Can I reset the stopwatch without losing my exported laps?
Yes. Exporting laps to CSV or copying them to the clipboard saves that data outside the browser's live session, so resetting the stopwatch afterward does not affect any laps that were already exported.
Summary
The Online Stopwatch times an activity to the nearest hundredth of a second, with lap recording that shows both elapsed time and the delta from the previous lap, and automatic highlighting of the fastest and slowest laps in a run.
Keyboard shortcuts for start and stop, lap, and reset support one-handed operation, and completed laps export as CSV for a training log. Elapsed time is derived from a stored start timestamp on every update, which keeps the display accurate through a backgrounded tab or a brief device sleep.