90 minute timer
The deep-work block. Ninety on, twenty off.
Time’s up.
Space bar starts and pauses · F goes full screen · the countdown survives a page refresh.
How to use this timer
- Press Start Or tap the space bar. The countdown keeps the right time even in a background tab or after a refresh.
- Pick a face Eight faces from the app, all free here. Your pick is remembered on this device.
- Go full screen Press F or the corner button to leave only the clock. Escape brings the page back.
Also: set a timer for 90 minutes · 90 min countdown · online 90 minute alarm.
What 90 minutes is good for
Ninety minutes is enough to load a hard problem into your head and still do something with it — roughly twenty minutes of loading and seventy of work. That arithmetic, not any ultradian rhythm, is the honest argument for the length. Protect it on the calendar before you try to protect it with willpower.
While the clock runs
- Add brown noise Generated in the browser — it never loops and never buffers.
- Study with me mode Full screen, nothing but the clock — for working alongside someone, or filming.
- Change the clock face Eight faces — minimal, neon, split-flap, LED. All free here.
- The full timer Four modes with breaks handled for you, and all eight clock faces.
Questions people ask
How do I set a timer for 90 minutes?
It is already set. The countdown on this page opens at 90 minutes — press Start, or tap the space bar. Nothing to install and no account.
Is a 90 minute block based on ultradian rhythms?
That is the popular explanation, and it is shakier than it sounds — the 90-minute cycle is well established in sleep and much weaker while awake. The honest argument is arithmetic: hard problems take about twenty minutes to load, so ninety leaves seventy minutes of actual work.
Does the timer keep running if I switch tabs?
Yes. The clock is worked out from the real time rather than counted frame by frame, so a background tab, a locked screen or a page refresh all resolve to the correct remaining time when you come back.
Will it make a sound when the time is up?
Yes, unless you turn off “Sound at the end”. Browsers block audio until you have interacted with the page, so the alarm works from the moment you press Start.
Can I use it full screen?
Press F or the icon in the corner. Full screen fills the display with the clock alone, which is what makes it readable from across a room or on a second monitor.
A browser tab can only do so much
This page keeps counting as long as it stays open. The iPhone and iPad app does the part a tab cannot: it blocks your distracting apps for the length of a session, keeps the clock on the Lock Screen and in the Dynamic Island, and turns finished sessions into streaks and a heatmap.
Worth saying plainly: the shield only covers apps on that iPhone. It has no opinion about the laptop open next to it.