Bursta

A free interval timer that runs in the browser. Pick a format, press Start, and a bell marks every round. Twenty pages, one per format: boxing, MMA, Tabata, EMOM, AMRAP, the Norwegian 4x4, box breathing and more, each with its sources. No install, no account.

Each page opens on that format's numbers, ready to start: boxing rounds of 3 minutes with a minute of rest, Tabata's 8 × 20/10, the Norwegian 4x4, a 7 minute workout circuit, box breathing, and 15 more. A bell marks every change, with a warning before a round ends. A big clock with a fullscreen key works on a phone, a laptop or a gym TV, and keeps the screen awake where the browser allows. Under each timer there is a short article on the format, with the sources behind its numbers.