Free Online Alarm Clock — Set Custom Alarms in Your Browser
Quick set
Common wake-up and reminder times. Click to jump straight to a preset alarm page.
How the online alarm clock works
Pick an hour, minute, and AM/PM. Choose a sound. Click Set Alarm. When the time arrives, the alarm rings in your browser and a full-screen overlay appears with the alarm message.
Will the alarm ring if my tab isn't active?
Yes — browsers throttle background tabs but timers and audio still fire reliably. We also flash the page title (⏰ ALARM!) so you'll spot it in your browser tab bar, and vibrate on mobile if your device supports it.
Does it work offline?
Once the page is loaded, yes. The alarm uses a JavaScript timer running in your browser, not a server call. Close the tab or shut down the computer and the alarm won't ring.
Will it wake my computer from sleep?
No — no browser-based alarm can wake a sleeping computer. Disable sleep mode or use your operating system's native alarm if that's a hard requirement.
How accurate is it?
The alarm fires within ~1 second of the target time. We re-sync every 30 seconds against the system clock to avoid drift.