A free 90 minute countdown timer. Ninety minutes aligns with the brain's natural ultradian rhythm — the reason many productivity researchers recommend 90-minute deep work blocks.
The timer is pre-set to 90 minute timer. Press the play button or hit Space to begin.
Click the settings icon to change font, colour, background, and size. All settings are encoded in the URL — bookmark it to reuse your exact setup.
Press F for fullscreen — ideal for classrooms and presentations. For streaming, enable transparent background and paste the URL into OBS as a browser source.
Research by Peretz Lavie and others shows the brain naturally cycles through 90-minute ultradian rhythms of high and low alertness. Working in 90-minute focused blocks and then resting aligns with this natural rhythm.