Just Set Alarm
How Online Alarms Work
Browser alarms are useful while a website remains open and the device is awake. They are not operating-system alarms, cannot work after the site is closed, and cannot guarantee a timely alert through device sleep or browser suspension.
Reviewed against the current app behavior on .
The Short Answer
Keep Just Set Alarm open, keep the device awake, and test the intended speakers or headphones before relying on an alarm. Use a native alarm or another device as a backup when missing the alert would matter.
How The Alarm Is Scheduled
Just Set Alarm uses the date, time, and time zone reported by your device. While the site is running, it checks scheduled alarms against the current time every second. It records a triggered occurrence so the same alarm does not ring repeatedly.
An alarm can trigger during the two minutes after its scheduled time. That short recovery window handles ordinary callback delays, but it does not make the alarm dependable through prolonged sleep or suspension. If the browser resumes after that window, the occurrence can be missed.
What Happens In Common Situations
| Situation | Expected Behavior |
|---|---|
| Another page on this site | The shared alarm runtime continues checking enabled alarms. |
| Background tab | The browser may slow the page, delaying the alarm or its sound. |
| Locked or sleeping device | The browser may be suspended, so the alarm can be late or missed. |
| Closed tab or browser | The alarm cannot run or make sound. |
| Page refresh | Saved alarms return, but browser audio may need a new interaction. |
How Alarm Sound Works
Alarm sounds are generated inside the browser with the Web Audio API; they are not downloaded audio files. Browsers can require a click or key press before allowing sound, particularly after a refresh or restored session.
The app uses full internal gain, but actual loudness is controlled by the device, browser, and selected audio output. Test the alarm through the same speakers, headphones, or Bluetooth device you intend to use.
Notifications Are Not A Backup Alarm
If notification permission is already granted, the site creates a browser notification when its alarm code triggers. It does not schedule an independent system notification in advance, so notification permission cannot make an alarm work after the site is closed or suspended.
What Is Saved In Your Browser
Alarm definitions are stored locally in the current browser. There is no account and no server-side alarm record, so alarms do not sync to another browser or device.
Dismissing a one-time alarm removes it. A repeating alarm remains scheduled for its selected days, and snoozing postpones the current occurrence. Alarm sound stops automatically after two minutes if you do not respond.
Before You Rely On An Online Alarm
- Set the alarm and confirm that it appears in the alarms list.
- Use Test Sound with the intended audio output connected.
- Keep this site open and leave the device awake.
- Keep the page in the foreground when possible.
- Use a native alarm or another device as a backup for important alerts.
Online Alarm Reliability FAQ
Related Browser Tools
Return to the online alarm clock, use the countdown timer for a duration, or open the online digital clock.