How accurate is this online clock?

It compares your device with the web server's UTC time several times and corrects the difference, usually to within ±0.05 seconds. The estimated error is shown under the clock.

Does the stopwatch keep running if I switch tabs?

Yes. Elapsed time is measured from the start moment, so it stays correct even if the browser slows down background tabs; the display catches up as soon as you return.

Is the time the same as a ticketing site's server time?

Most ticketing and registration servers are synced to standard time, so they match closely, but individual sites can differ by tens to hundreds of milliseconds. An early alert of 0.2–0.3 seconds helps cover click and network delay.

Online Stopwatch & Timer

A stopwatch with laps, a countdown timer with alarm and a millisecond clock corrected to server time. Works on phones and desktops, no install.

—

--:--:--

Syncing with server time…

12-hour clock Milliseconds

Stopwatch

00:00.000

Space start/stop · L lap · R reset

Countdown timer

hours

minutes

seconds

05:00.0

Beeps and flashes when time is up. Keep this tab open.

Countdown to an exact time (ticket sales, launches, registration)

Alert Beep for the last 5 seconds Flash the screen

--HOURS

--MIN

--SEC

-1/10

Click now!

Uses your local time, corrected with the server offset above. Press Start once so the browser allows sound. The early alert gives you a head start for click and network delay.

World clock

How this online stopwatch and clock work

Server-synced clock. When the page opens it repeatedly asks the web server for its time (the HTTP Date header, which servers keep aligned to UTC) and catches the exact moment the server's second ticks over. From that it works out how far your device clock is ahead or behind, corrects the display and shows the estimated accuracy — usually within ±0.05 s. It re-syncs every 10 minutes.

Stopwatch uses your browser's high-resolution timer, so it keeps running accurately even if the system clock changes. Lap times show the split for each lap and the running total; the fastest lap is green and the slowest red. Countdown timer counts down a duration and beeps when it reaches zero. Countdown to an exact time is built for ticket sales or class registration that opens at a precise moment.

If your device clock is off by more than a second, turn on automatic time: on Windows go to Settings → Time & language → Date & time → Sync now; on phones enable “Set time automatically”.

Frequently asked questions

How accurate is this online clock?: It compares your device with the web server's UTC time several times and corrects the difference, usually to within ±0.05 seconds. The estimated error is shown under the clock.
Does the stopwatch keep running if I switch tabs?: Yes. Elapsed time is measured from the start moment, so it stays correct even if the browser slows down background tabs; the display catches up as soon as you return.
Is the time the same as a ticketing site's server time?: Most ticketing and registration servers are synced to standard time, so they match closely, but individual sites can differ by tens to hundreds of milliseconds. An early alert of 0.2–0.3 seconds helps cover click and network delay.