What this online alarm clock does
This tool turns your browser tab into a working alarm clock. Set a time, an optional label, and whether it should ring once or every day, and it arms instantly — no account, no app store, nothing to install. The live clock ticks in real time so you always know exactly where you stand against your next alarm.
It's built for the moments a phone alarm is overkill or inconvenient: a reminder while you're already at your desk, a recurring daily prompt, or a quick one-off wake-up for a nap or a call. You can stack several alarms at once, each tracked independently.
How to use it
Four steps — the alarm rings as long as this tab stays open somewhere in your browser.
- Set the alarm time.Pick it from the clock or type it, in 12-hour or 24-hour format.
- Name it and choose repeat.A label is optional but helpful once you have more than one alarm running.
- Click Add alarm.It appears in your list below, armed and counting down in the "Time remaining" metric.
- Leave the tab open.When the time hits, it rings with sound and an on-screen alert — snooze it for 9 minutes or stop it entirely.
How the alarm is triggered
The page checks the current time against every armed alarm once a second. The moment the clock reaches an alarm's set time, it rings — no server round-trip, no push notification, just your browser's own clock compared against the time you chose.
6:51:30 AMAlarm time:
7:00:00 AMTime remaining = 7:00:00 − 6:51:30 = 8m 30s
At 7:00:00 AM the clock matches and the alarm rings.
Once vs. every day
A once alarm rings a single time and then removes itself from your list. An every day alarm keeps re-arming for the same time tomorrow, and the day after that, until you switch it off or delete it.
Snooze
Pressing snooze stops the sound and re-arms that exact alarm for 9 minutes later — the same interval used by most physical alarm clocks — without disturbing its label or repeat setting.
Quick examples
Common ways people use a browser-based alarm.
| Scenario | Alarm time | Repeat |
|---|---|---|
| Weekday wake-up | 06:45 | Every day |
| Take medication | 09:00 | Every day |
| Leave for a meeting | 13:15 | Once |
| End a work session | 17:30 | Once |
Prefer to count down a stretch of time rather than pick a clock time — "in 20 minutes," for instance? The countdown timer is built for exactly that, and the stopwatch handles the reverse: timing how long something takes.
Who uses it, and for what
- Remote workers setting a recurring reminder to stand up, take a break, or join a call.
- Students waking up for an early class or timing a study block without reaching for their phone.
- Anyone at a desk who wants a one-off nudge — a nap, a delivery window, a pot on the stove — without digging out a physical timer.
- Shift workers checking what a scheduled alarm time looks like across 12-hour and 24-hour notation. See the military time converter if a 24-hour value looks unfamiliar.
Planning your sleep window around a fixed wake-up time? The sleep calculator works backward from an alarm time to suggest when to go to bed.
Frequently asked questions
Does the alarm still ring if I close the tab?
No. The alarm runs entirely in this browser tab, so it can only ring while the tab is open — it is not a background app or a phone alarm. Minimising the window or switching to another tab is fine; closing the tab or the browser is not.
Can I set more than one alarm?
Yes. Add as many as you need, each with its own time, label, and repeat setting. Every armed alarm is checked independently, so several can be active at once.
What does snooze do, and how long is it?
Snooze silences the current ring and re-arms that same alarm for 9 minutes from the moment you press it — the traditional snooze interval on most physical alarm clocks.
What's the difference between "once" and "every day"?
A "once" alarm rings a single time and then removes itself from the list. An "every day" alarm rings at the same time daily until you switch it off or delete it.
I set an alarm for a time that's already passed today — when does it ring?
It arms for the next occurrence of that time, which will be tomorrow. Setting a 07:00 alarm at 3:00 PM does not ring immediately — it rings at 07:00 the next morning.
Will it still ring if the tab is in the background?
In most cases yes, but browsers slow down inactive tabs, so the alarm may ring a few seconds late rather than not at all. For anything time-critical, keep the tab active and your device volume up.
Is it free, and is my data private?
Completely free with no sign-up. The clock and every alarm run locally in your browser — nothing is uploaded or stored on a server.
Accuracy & sources
The alarm is triggered by comparing your device's own system clock to the time you set, once a second, entirely inside your browser — there is no server-side scheduler and no data sent anywhere. That logic, including the snooze and repeat behaviour, has been tested by hand across on-time, late, and already-passed alarm times.
Times are read and displayed using the 24-hour clock notation defined by ISO 8601, the international standard for representing dates and times, alongside the familiar 12-hour format. Written and reviewed by Fletcher Langley, and re-checked whenever the tool changes — last reviewed August 2026.
About the author
Operations and workforce-systems specialist with 14+ years inside shift-based industries and payroll platforms, and a BS in Industrial Engineering. Fletcher writes and reviews the calculators, converters, and guides here — from overnight-shift math to decimal payroll hours — drawing on years spent translating between 12-hour, 24-hour, and military time for real timesheets.
Written & reviewed by Fletcher Langley · Last updated: August 2026