Does an Online Stopwatch Keep Running in a Background Tab?

The short answer

Yes. The Lazyblink Stopwatch keeps counting when you switch tabs, minimise the browser, lock your screen or let your computer sleep, because it does not count ticks; it records the moment you pressed Start and subtracts that from the current time. The display may update less often while hidden, but the time is correct the moment you look again. What does stop it: closing or reloading the tab, pressing Reset, switching to the Countdown tab (which pauses it), or the browser unloading the tab to save memory.

How this stopwatch measures time

Many people assume a web stopwatch adds 10 milliseconds every time a timer fires. If it worked that way, any delay would make it fall behind. This one does not.

When you press ▶ Start, the code notes the current clock time. About every 10 ms it reads the clock again and shows the difference. When you press ⏸ Pause, it remembers the time elapsed so far. When you press Start again, it continues from that amount.

So the number on screen is always "now minus when you started, minus any paused time". A late or skipped update changes how smoothly the digits move, never the result.

What happens in common situations

You do this	Does timing continue?	What you see when you return
Switch to another tab	Yes	Correct elapsed time
Minimise the browser	Yes	Correct elapsed time
Lock the screen	Yes	Correct elapsed time
Laptop sleeps, then wakes	Yes, the sleep time is included	Time jumps to the correct total
Click the Countdown tab	No, it pauses	Time frozen where you left it
Press Reset	No, cleared	00:00.00 and laps deleted
Reload or close the tab	No, lost	00:00.00

Why the display slows down in the background

Browsers save battery by limiting timers in pages you cannot see. Google's Chrome team documents three levels. A hidden page's timers are normally checked only once per second. After a page has been hidden for more than five minutes, has been silent for at least 30 seconds and keeps scheduling repeated timers, Chrome can switch to intensive throttling, which checks timers only once per minute.

For this stopwatch, that only means the hidden display is updated less often. Since each update reads the real clock, the first update after you come back shows the right total.

Sleep is counted, not skipped

Because the stopwatch compares clock times, the minutes your computer spent asleep are included. That is usually what you want for timing a cooking job, a workout or a meeting. If you wanted to exclude a break, press Pause before closing the lid.

What actually loses your time

Closing or reloading the tab

The elapsed time and laps live only in that open page. Nothing is saved to your browser or a server, so a reload starts from zero. If you need a record, write the times down or copy them before closing.

Switching to Countdown

The widget has two tabs, Stopwatch and Countdown. Clicking either tab stops whatever is running. Your stopwatch reading stays on screen when you come back, so press Start to carry on from where it paused.

The browser discarding the tab

Phones and low-memory computers sometimes unload tabs you have not looked at for a while. When you return, the page reloads and the stopwatch shows zero. To reduce the risk on a phone, keep the stopwatch tab in front, plug in the charger for long sessions, and avoid opening many heavy apps at the same time.

Changing the computer's clock

The stopwatch trusts your device clock. If the clock is changed while you are timing, for example by manually setting a new time, the reading jumps by the same amount. Ordinary use does not do this.

Tips for long timings

• Keep the tab in its own window if you need to glance at it while working in other tabs.
• Use Lap for checkpoints. Each lap stores the total time at that moment, newest at the top. To get the time for one lap alone, subtract the previous lap's total. How to Time Laps With an Online Stopwatch and Work Out Split Times walks through that.
• Note the time on paper for anything important. A browser tab is convenient but not a permanent record.
• Hours are shown automatically. Under an hour the display reads minutes, seconds and hundredths (for example 12:04.37). Past an hour it adds the hour at the front (1:12:04.37).

How accurate is it?

The stopwatch reads the device clock in milliseconds and shows hundredths of a second. The display refreshes roughly every 10 ms while visible, so the last digit is a little behind the true value at any instant, and your own reaction time when pressing Start and Pause is usually a much bigger source of error. For everyday timing, such as workouts, presentations, cooking and study sessions, it is more than precise enough. For official sport timing, use dedicated equipment.

Stopwatch or Pomodoro timer?

A stopwatch counts up from zero with no end. If you are timing focused work sessions with planned breaks, a dedicated Pomodoro Timer is built for that rhythm and saves you from watching the clock.

Quick troubleshooting

The digits look frozen

You are probably looking at a paused stopwatch. Check whether the main button says ▶ Start (paused) or ⏸ Pause (running).

The Lap button is greyed out

Lap only works while the stopwatch is running. Press Start first.

My laps disappeared

Pressing Reset deletes all laps along with the time. So does reloading the page.