Stopwatch

This is a stopwatch that runs in your browser. Press 'Start' and it counts up from zero, showing hundredths of a second in a minutes:seconds.hundredths format. You can pause at any time, press 'Lap' while it runs to record the current time, and export the lap list as a text file. It suits everyday timing, such as a run, a speech, a set of exercises or the steps of an experiment. Two things up front. First, it is not professional timing equipment, and its accuracy depends on your browser and device, so it is not for situations that need rigorous measurement. Second, each lap shows both a 'Split' (the difference from the previous lap) and a 'Total' (the time since you started) column. That is explained in detail below.

How to use it

1. Click 'Start' and the large display begins increasing from 00:00.00 in minutes:seconds.hundredths.
2. While it runs, click 'Pause' to stop. Clicking the same button again (now labelled 'Start') resumes from where it stopped without resetting.
3. Click 'Lap' while the stopwatch is running to add an entry to the 'Lap times' list. The newest entry is at the top. Each entry has three columns: the lap number, the split (the difference from the previous lap; for the first lap it is the time since the start) and the total (time since you started). The Lap button is disabled while the stopwatch is paused or not started.
4. Click 'Reset' to stop, set the time back to zero and clear all laps.
5. When there are laps, an 'Export' link appears next to the 'Lap times' heading. It downloads a text file called lap-times.txt with a header row, then one line per lap from the first to the last, with the lap number, split and total (minutes:seconds.hundredths) separated by tabs.

What a lap records: an illustration

Imagine you are running laps on a track and press 'Lap' at the end of each of three laps. Suppose the stopwatch reads 01:00.00 at the first press, 02:30.00 at the second and 04:00.00 at the third. The 'Total' column then shows 01:00.00, 02:30.00 and 04:00.00, while the 'Split' column shows 01:00.00, 01:30.00 and 01:30.00. A split is that lap's total minus the previous lap's total, and for the first lap it equals the total. These numbers are only there to illustrate the idea and are not real measurements. It works like the 'lap' and 'total' columns on a phone stopwatch.

Supported scope and known limits

• The display format is minutes:seconds.hundredths with no hours digit. Past 60 minutes the minute count keeps rising; 75 minutes appears as 75:00.00.
• The tool does not mark the fastest or slowest lap. A split is the difference between neighbouring laps, and paused time is not part of the elapsed total, so a lap that spans a pause only includes the time the stopwatch was actually running.
• The display is worked out from a start timestamp on the system clock: current time minus the start time, plus the milliseconds accumulated before the last pause. So even if you switch to another tab and the display stops refreshing, the correct elapsed time is shown when you return. The stopwatch state (whether it is running, the start timestamp, accumulated time and laps) is kept in your browser's local storage, so after moving to another tool on this site, or reloading or closing and reopening the page, a running stopwatch carries on and a paused one stays at the same value. 'Reset' clears this state.
• Screen refresh rate depends on the device. A lap stores the value shown at the time of your click, so an error of a frame or two (typically tens of milliseconds) is normal. Do not use it to judge results at the millisecond level.
• There is no sound and no long-term history. Laps are stored only with the current stopwatch state and are cleared by 'Reset', so use 'Export' if you want to keep them.
• The exported file is plain UTF-8 text. If some older program shows the Chinese title incorrectly, open it as UTF-8.

FAQ: How is a stopwatch different from a countdown timer?

A stopwatch counts up from zero to show how long something took. A countdown counts down from a length you set and alerts you at zero. If you want the page to ring when time is up, use this site's Countdown Timer.

FAQ: If I pause and restart, will the time be wrong?

No. When you pause, the tool stores the time accumulated so far, and when you press 'Start' it only adds from the new starting point, so the paused period is not counted. If you pause at 00:30.00 and resume ten minutes later, the display carries on from 00:30.00.

FAQ: How do I find how long each lap took?

Read the 'Split' column, which is already the difference from the previous lap. If lap 1 totals 01:00.00 and lap 2 totals 02:30.00, lap 2's split is 01:30.00. The exported file has both columns too.

FAQ: How accurate is it?

The display resolution is a hundredth of a second, but real accuracy depends on your browser and device. It measures against the system clock, so error does not build up over time, but screen refresh and click response both have some delay. That makes it fine for everyday use and unsuitable for official competition timing.

Privacy and processing

The stopwatch runs entirely in your browser. Nothing in the code sends your timing or lap data to a server. So that timing can continue after you change page or reload, the stopwatch state (start timestamp, accumulated time and laps) is kept in your own browser's local storage; 'Reset' or clearing site data deletes it. The export file is generated locally by your browser and downloaded.