Zero made intermittent fasting feel simple: pick a plan, start the clock, watch the ring fill. That core is a timer and a calendar, and it does not need an install or an account to work. So we built Fast Clock, a free fasting timer that runs right here in your browser. It opens with a 16:8 plan already running, updates every second, and keeps your streak on your device.
Start your fasting clock
Pick a plan, then set when your fast starts or when you plan to eat. The ring, the countdown and the stage list all move as you change it.
How to use it
Choose 16:8, 18:6, 20:4 or OMAD. The number before the colon is fasting hours, the one after is your eating window. Then set either time: change “Fast starts” and the first-meal time follows, or set “Fast ends” and the start follows. The big ring shows time left in your fast, or time left to eat once the window opens.
Choose 5:2 to plan two low-intake days a week instead. Tap any day to move one of them.
Tap the log button after a fast finishes. Log on consecutive days and the streak counter grows; miss a day and it restarts. The 14-day grid shows what you logged. Everything is stored on your device and nothing leaves your browser. The speaker icon turns on a soft chime and starts muted.
The stage list under the ring is general background on what people commonly describe at different points of a fast. It is not medical advice.
How it compares to Zero
Fast Clock keeps what makes Zero’s timer useful: a live ring, named plans, an eating-window countdown, a fasting stage timeline and a streak. The start and end times are editable, so it fits a real schedule and not only a fixed 16:8.
We left out most of what makes the full app a daily companion. Zero has a library of guided plans, body and weight logging, mood and hunger notes, educational content, charts over months, reminders and syncing across devices. Some of that sits behind a subscription. Fast Clock has no account, so it cannot remind you or sync, and closing the tab does not send you a nudge.
Use Fast Clock when you want a timer open in a tab right now, or you are trying intermittent fasting before committing to an app. Get Zero when you want reminders, long-term tracking and guidance.
Get the full app
Zero - Intermittent Fasting is on Android with a free tier and optional paid features. Its own site is zerolongevity.com.
Frequently asked questions
Is this the real Zero app?
No. Fast Clock is an original tool we built, inspired by the fasting timer in Zero - Intermittent Fasting. We are not affiliated with, endorsed by, or connected to Zero or its publisher. For reminders, long-term tracking and guided plans, get the real app from the links above.
Can I use a fasting timer in a browser without downloading anything?
Yes. Fast Clock needs only a browser tab, on a phone or a computer. There is nothing to install and no account to create.
Does it work offline?
Yes. Once the page has loaded it runs on your device, and your streak and history are stored locally. Because it cannot send notifications, keep the tab open or check back when your eating window is due.
Is it free?
Yes, with no signup and no limits on plans, logs or streaks.
Is intermittent fasting safe for everyone?
No. Fasting is not right for everyone, including people who are pregnant, have diabetes, take medication, or have a history of disordered eating. Fast Clock is a timer, not medical advice, so talk to a doctor before starting.
