منبه عبر الإنترنت.

The tab must stay open, the sound on and the computer awake; sleeping devices do not ring. Use your phone’s alarm for important wake-ups.

The next occurrence of the chosen time is computed (today or tomorrow) and checked twice a second; the chime is synthesised with the Web Audio API.

An alarm set at 23:00 for 07:00 shows “in 8 h 0 min” and rings the next morning if the computer stays awake.