Alarm Clock

No — full system sleep suspends browser timers, which is the honest limit of every web alarm. The tool requests a screen wake lock (supported in most modern browsers) to keep the display on while armed, but a closed laptop lid overrules everything. Plugged in, lid open, volume up, tab open: that's the checklist.

Browsers block audio that no user ever gestured for — the rule that stopped autoplaying video ads. Clicking Set counts as your permission and initializes the audio engine inside that gesture, so the tone is allowed to fire later even if you've been in another tab for hours.

As a second system: your phone alarm plus this one means a dead phone battery doesn't cost you a flight. Beyond backup: desk naps, timeboxing work sessions, meeting reminders on a machine where you can't install apps, and kitchens where the laptop is already open. For sole-alarm duty on important mornings, a phone or hardware clock is still the right tool.

They're synthesized in real time with the Web Audio API — oscillators shaped into a classic beep, a chime arpeggio, or an urgent pattern. No audio files means nothing to download or fail to load, it works offline once the page is open, and the sound starts instantly at full reliability.