Interval & Tabata Timer

Why the beeps never miss

The whole workout is one fixed schedule: start it and every beep has a known moment, down to the millisecond. Those moments are handed to your browser's audio clock well in advance, and the audio clock keeps running while a background tab is slowed down — so the beep for "work is over" arrives exactly on time, even if the browser had quietly parked this page. When you come back, the display catches up instantly.

You hear a high beep when work starts, a lower one when rest starts, three short ticks before every phase change, and a finish chime at the end. The beeps need one interaction with the page first (pressing start is enough) because browsers only let a page play sound after you have engaged with it. Skip jumps to the next phase; everything still runs on the original clock. Nothing here touches the network.