Online Clock — Full Screen Digital Clock with Seconds

A free, full-screen digital clock for your browser — accurate, customizable, and distraction-free.
An online clock is a clock that runs in your web browser instead of on a wall, watch, or operating-system tray. It uses the time signal already inside your device — synchronized in the background by your OS to internet time servers — and displays it in a large, readable, customizable format. No installation, no account, no syncing of its own. Just open the page and you have an accurate clock.
People reach for an online clock for the same reasons they used to glance at a wall clock: a visible, persistent reference that doesn't require pulling out a phone or peeking at a tiny menu-bar widget. The difference is that a browser-based clock can be huge, theme-able, and one keystroke away from full screen.
The same big readable clock works in very different contexts. A few of the most common:
The clock you see here is read from your device's system clock — the same clock your OS shows in the menu bar or notification area. Modern operating systems keep that clock synchronized using Network Time Protocol (NTP), which traces back to atomic clocks at official time labs (NIST in the United States, NPL in the United Kingdom, PTB in Germany, and others). Once your OS has done its part, a browser-rendered clock is typically accurate to within a few hundred milliseconds of true atomic time.
For practical use cases — meetings, exams, classroom timing, kitchen cooking, OBS overlays — that's vastly more precision than is needed. If you suspect your clock is drifting, the fix is at the OS level (re-sync system time), not in the browser.
The clock can display either format. 12-hour (with AM/PM) is standard in the United States, Canada, the Philippines, and a few other regions. 24-hour (also called "military time") is the international standard and is the default in most of Europe, Latin America, Asia, and Africa. Toggle between them in the settings panel — your choice is remembered.
The clock follows your device's time zone settings, which means it automatically jumps forward in spring and back in autumn for any region that observes Daylight Saving Time (DST). If you've set the clock to a specific city via the settings, that city's local DST rules apply — not your own. Cities that don't observe DST (most of Asia, most of Africa, Hawaii, Arizona, the equatorial zone) stay on the same offset year-round.
The journey from sundials to the online clock you're reading is one of the most interesting strands in the history of measurement. Sundials (around 1500 BCE) measured the day by the position of a shadow. Water clocks (clepsydras) followed, then mechanical escapement clocks in medieval Europe — early ones drifted by 15 minutes a day. The pendulum clock (Christiaan Huygens, 1656) cut that to seconds per day. Quartz oscillators in the 1920s reached parts per million accuracy. Modern cesium atomic clocks are stable to better than one second in 100 million years.
A browser clock is at the very far end of that line: software running on a device that pulls its time from a network of atomic clocks, displayed on whatever screen happens to be in front of you. The same precision used to coordinate satellites and stock markets, in a tab.
Once you have the time, you often need to do something with it. A few related tools:
Free customizable clock widgets — pick a style:
Yes, within the limits of your device. The clock reads the system time of the device you're using, which most operating systems sync to NTP (Network Time Protocol) servers — the same source ultimately traceable to atomic clocks. Browser-rendered clocks are usually accurate to within a few hundred milliseconds. For most uses (meetings, exams, cooking, classroom display) that is far more precise than needed.
Yes. Click the Fullscreen button on the dock and the clock fills your entire monitor — perfect as a screensaver, classroom display, or kitchen wall clock. Press Esc to exit.
Yes. Open the settings panel (sliders icon) and toggle Show Seconds, 12-Hour Format, Show Date, and Show Location independently. Your preferences are saved in your browser.
Yes. The location selector inside settings lets you pick any IANA time zone — for example, set the clock to Tokyo while you're in New York. Daylight Saving Time is handled automatically.
Yes. Theme, format, time zone, and toggle settings are saved in browser local storage. They'll be restored next time you open the page in the same browser.
Yes — the clock is free, no account required. You can also embed our analog, digital, text, or word clock widgets on your website with a single embed code.
Once the page is loaded, the clock continues to tick from your device's internal time even if you lose internet. Reconnecting will not change the visible time unless your system clock has drifted.
Yes. The interface is responsive and works in iOS Safari, Android Chrome, and on tablets. You can pin it to your home screen for one-tap access.
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