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Timer data stays on this device. Google Analytics can send cookieless signals before your choice or after decline. Your choice controls analytics storage; change it on Privacy. Privacy Policy

Free intermittent fasting timer

Set a 16:8 timer in your browser. See elapsed and remaining time; keep history on this device. Free, no account or download.

  • No app
  • No account
  • Local history
  • Works offline

Free, no account, no app. Your timer and history stay in this browser.

Timer not running00:00:00
  1. Fed
  2. Early fasting
  3. Fuel-use context
  4. Ketone context
  5. Longer fasting
Your on-device data

Back up, restore, or erase the timer data stored in this browser. Nothing is sent to a server.

Planning estimates only — see methodology for phase sources. Not medical advice.

Using the timer in everyday situations

Your timer uses the saved start time on this device. These answers explain what is saved and what needs an open tab or a connection.

I forgot to start the timer. Can I correct the time?

Start the timer, choose Edit start time, and enter the time of your last meal. It uses today, or yesterday if that clock time is still in the future. This control cannot select an earlier date. For an entry already in history, use Correct times on that entry.

What happens if I close the tab?

Reopen this site in the same browser and profile. If local storage is available, the timer restores the session and calculates elapsed time from its saved start. Reaching the target does not end or save the session automatically. Completion alerts require permission and an open tab; they are not background alarms.

Can I use it without an internet connection?

Open this page online and let it finish loading, then reload it once while you still have a connection. Previously visited pages can then reopen offline after the service worker has cached them; pages you have not visited may need a connection. Check that the timer reopens offline before relying on it. An offline timer does not provide background alerts.

How do I move my timer or history to another browser?

Open Your on-device data, download a backup, and restore that JSON file in the other browser. Restoring replaces the timer data already saved there. Keep the file private: it includes your session, history and preferences. There is no account sync. If browser data is cleared or storage is unavailable, recovery requires a backup.

Find local backup controlsCheck calculations and limitations

How the fasting timer works

Choose a schedule, start the timer, and track elapsed and remaining time. The phase timeline uses illustrative hour markers; a clock cannot measure your insulin, ketones or autophagy.

  1. Pick a protocol

    Compare eating windows with your actual meal times. A schedule label does not establish medical suitability.

  2. Start with one tap

    The timer runs right in this browser — no download, no account. Your session and history stay on this device.

  3. Track time, understand the limits

    See elapsed time and educational reference markers. End or adjust the fast whenever needed; completing a longer window is not a health requirement.

Educational fasting timeline

  • Fed

    reference marker: 0h

  • Early fasting

    reference marker: 4h

  • Fuel-use context

    reference marker: 12h

  • Ketone context

    reference marker: 16h

  • Longer fasting

    reference marker: 24h

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