What the Alarm Clock Online does
This online alarm clock rings at a time of day you choose, right in your browser: set one or several alarms, give each a label, repeat them on chosen weekdays, pick a sound and a volume, and snooze or stop when it rings. A large clock shows the current time and a countdown to the next alarm. Nothing is installed and nothing you set leaves the tab.
Because it runs in a web page, it only works while the tab stays open and the computer stays awake - closing the tab, quitting the browser or letting the device sleep silences it. It is handy for a nap at your desk, a reminder while you work or a wake-up alarm on a laptop that stays on, but for anything you cannot afford to miss, use your phone's built-in alarm as well.
How to use it
- Choose the alarm time and, if you like, a label such as "Wake up" or "Call the bank".
- Tick the weekdays it should repeat on, or leave them all unticked for a one-off alarm.
- Pick a sound, set the volume and press Test sound - browsers only allow a page to play sound after you have clicked on it, and this also checks your speakers are on.
- Press Add alarm. Add more if you need them; the list shows when each one will ring and the big countdown shows the next.
- When it rings, press Stop, or Snooze to ring again after the snooze length you chose. Tick "Remember my alarms" to keep them for your next visit, and "Keep the screen on" so a laptop or tablet does not go to sleep.
Reading the results
Times follow this device's clock and time zone, including daylight-saving changes. If your computer's clock is wrong, the alarm is wrong in the same way.
A one-off alarm switches itself off after you press Stop; a repeating alarm re-arms for the next day it applies to. Snoozing pushes the ring time back by the snooze length from the moment you press it.
If the computer slept or the browser paused the tab, the alarm rings as soon as the page can run again and says how late it was. A late ring means the tab could not run on time - it is the signal to keep the device awake next time.
Worked example: a weekday wake-up alarm set on a Friday evening
It is 22:00 on Friday 23 October 2026. You set 06:45, repeating Monday to Friday, labelled "Work". Saturday and Sunday are skipped, so the alarm is armed for Monday 26 October at 06:45 and the countdown reads 2 d 8 h 45 min.
On Monday it rings at 06:45. You press Snooze with a 9-minute snooze at 06:45:10, so it rings again at 06:54:10. You press Stop, and because it repeats on weekdays it re-arms itself for Tuesday at 06:45.
A separate one-off 20-minute nap alarm set at 14:10 rings at 14:30 and then switches itself off.
How this differs from the Online Timer
The Online Timer counts down a length of time - 25 minutes, say - and beeps at zero. This alarm clock rings at a time of day, such as 07:00, can hold up to ten alarms with their own labels and repeat days, offers snooze and a choice of sounds, and shows a large clock with the time left until the next alarm.
Why browser alarms need the tab open
Web pages cannot wake a sleeping computer or run after their tab is closed - that is a deliberate browser rule, not a limit of this page. To save battery, browsers also slow down timers in background tabs. This alarm clock reads the real time from the device clock on every tick instead of counting ticks, so a slowed tab never drifts: it can only be late, and it tells you when it was.
For the best chance of ringing on time: keep the tab open (it can be in the background), plug the laptop in, turn off sleep while the alarm is set or tick "Keep the screen on", and turn the system volume up. Some browsers mute tabs that have never been clicked, which is why the page asks for one click first.
Limitations: what the result does not prove
- It cannot ring if the tab is closed, the browser quits, the battery dies or the device sleeps. It is not a substitute for a phone or bedside alarm when missing it matters.
- Sound depends on your device volume, speakers or headphones and the browser allowing audio; the page cannot override a muted system.
- Alarms are kept only in this tab unless you tick Remember, and then only in this browser on this device.
- A ringing alarm stops on its own after 10 minutes so a forgotten tab does not ring all day.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- MDN - Web Audio API
- MDN - Autoplay guide for media and Web Audio APIs
- MDN - Screen Wake Lock API
- MDN - setTimeout: reasons for delays longer than specified (background tab throttling)
Frequently asked questions
Will the online alarm clock work if I close the tab or my computer sleeps?
No. A web page can only run while its tab is open and the device is awake. Keep the tab open, stop the computer from sleeping or tick Keep the screen on, and use a phone alarm as a backup for anything important.
Why can't I hear the alarm sound?
Browsers block sound until you have clicked the page once, so press Test sound after opening it. Then check the system volume, the browser tab is not muted, and the right speakers or headphones are selected.
Can I set more than one alarm at a time?
Yes, up to ten. Each has its own time, label, repeat days and sound, and the list shows when each one will ring next. The big countdown always shows whichever alarm comes first.
How do I set an alarm that repeats on weekdays only?
Tick Monday to Friday before pressing Add alarm. When you stop it on a Friday it re-arms for the following Monday. Leave every day unticked for an alarm that rings once and then switches off.
How does snooze work on this alarm clock?
Snooze silences the alarm and rings it again after the snooze length you chose - 5, 9, 10, 15 or 30 minutes - counted from when you pressed it. You can snooze as many times as you like; Stop ends it.
Does the alarm clock remember my alarms next time?
Only if you tick Remember my alarms in this browser. They are then saved on this device, not online, and alarms whose time passed while the page was closed are moved to their next time rather than ringing on arrival.
Which time zone does the online alarm use?
Your device's own clock and time zone, shown under the result, including any daylight-saving change. If you travel, the alarm follows your computer's clock once it has updated to the new zone.
Last reviewed by the A2Z.Tools team against the sources listed above.
