Fasted FASTED

Free Online Fasting Timer

Start a real fasting countdown right in your browser. Track your metabolic phases, see when you enter fat burning and ketosis, and get notified at every milestone. No app needed.

00:00:00 Waiting

Why use an online fasting timer?

Intermittent fasting is one of the simplest and most evidence-backed approaches to improving metabolic health, but knowing where you are in your fast makes a real difference. This free browser-based fasting timer shows your elapsed time, remaining time, and current metabolic phase so you can fast with confidence.

Your body transitions through five distinct phases during a fast: Fed State, Catabolic, Fat Burning, Ketosis, and Deep Ketosis. Each phase comes with different metabolic benefits. By seeing exactly when you cross each threshold, you can make informed decisions about when to break your fast and maximize the benefits you are after.

This timer runs entirely in your browser. Your data is saved in localStorage so it persists across page reloads. No account, no download, no tracking. For the full experience with streaks, history, and push notifications, try the Fasted app.

Frequently Asked Questions

Does the fasting timer still work if I close the browser tab?
Yes. Your fast start time is saved locally, so when you reopen the page the timer picks up exactly where you left off. No data is lost if you close the tab or restart your browser.
What are the fasting phases shown on the timer?
The timer displays metabolic phases your body moves through during a fast: the fed state, early fasting (blood sugar normalisation), the fat-burning zone (lipolysis), ketosis, and deep autophagy. Each phase is shown as you reach it in real time.
Can I use a custom fasting protocol with this timer?
Absolutely. You can set any fasting and eating window duration you like. Whether you follow 16:8, 18:6, 20:4, OMAD, or a completely custom schedule, the timer adapts to your chosen protocol.
Can I use this as a water fasting timer?
Yes. A water fast is just a fast with nothing in it but water and electrolytes, so the same clock and the same phases apply — set your target length and the timer counts it down. For a water fast of a day or more, use the extended fast planner instead: it runs the same timer but places electrolyte checkpoints through it and plans how you break the fast, which is the part that matters most on a multi-day fast.
Does the timer save my fasting progress and history?
The browser-based timer saves your current fast locally. For full history tracking, streaks, and long-term progress charts, download the Fasted app which syncs your data across devices.
How do I get notified when my fast ends?
Allow browser notifications when prompted and the timer will send you an alert the moment your fasting window is complete. You can also set reminders for upcoming eating windows.

Go deeper

science · 10 min read

What Happens to Your Body When You Fast (Hour by Hour)

A detailed hour-by-hour timeline of what happens in your body during a fast -- from 0 to 72 hours. Understand the science behind every stage of fasting.

getting started · 8 min read

How to Start Intermittent Fasting (Step by Step)

A practical step-by-step guide to starting intermittent fasting. Choose your schedule, set your window, and build the habit.

fasting methods · 7 min read

16:8 Intermittent Fasting: The Most Popular Schedule Explained

Learn how 16:8 intermittent fasting works, what the science says, and how to build a sustainable 16-hour fasting routine. Complete guide with meal timing tips.

More Free Tools

Fasting Zone Tracker

Interactive fasting zones chart showing what happens to your body at every hour. See when fat burning, ketosis, and autophagy begin.

Does It Break a Fast?

Search any food or drink and get a straight answer for three goals: strict fasting, fat loss, and autophagy. Calories, the reason, and the honest gray zones.

Fasting Calculator

Calculate your ideal fasting and eating windows based on your schedule, sleep time, and lifestyle. Get a personalised daily timeline.

Track fasting streaks and history in the Fasted app

The Fasted app saves every fast automatically, builds your streak calendar, and shows detailed stats so you can see your consistency improve over time.

Download on the App Store Get it on Google Play

Free to use — no account required