FairFast
Every schedule, from 13:11 to 72h+
Start a fast in one tap. 16:8, 18:6, 20:4, OMAD or your own goal, up to a full week for extended and water fasts.
Intermittent fasting tracker · iPhone & Android
The honest intermittent fasting tracker.
A fasting timer with no ads, no account and no locked history. What's free today stays free.
No adsNo sign-upLog stays on your phonePay once option
Try it · live
FASTED
12:29
EAT IN
03:31
NOW 08:29
Your eating window opens at 12:00. Stage 3: fat burning.
Started20:00
Goal16H
Stage3/5
The day tape
Your whole day in one line.
No rings to decode. One tape, three marks, and you know where you are and when you can eat.
Black is done
Time you've already fasted. It only ever grows.
Orange is now
Time left to your goal. The one thing to watch.
Hatched is food
Your eating window, so you know exactly when it opens.
Free, forever
Everything you need to fast. Nothing locked.
The timer, every schedule, widgets and your full history are free. No trial that runs out, no ads, no sign-up.
Your fast on your home and lock screen
Every fast you've logged. Never locked.
Month and year views. Edit any fast.
A daily schedule with reminders
Get a nudge when it's time to start and when your window opens. Skip a day when life happens.
See when you fast, at a glance
Water and weight in the same place
Add a glass from the timer. Log your weight when you want to, and never when you don't.
Export to CSV, any time
Your fasts, weight, water and missions in a plain file you can open anywhere. Free, always.
Fasting stages, with sources
What may be happening, hour by hour.
FairFast shows five typical stages of a fast. Every line is limited to what its sources say, and your body may be earlier or later.
- 0–4 h
Digesting
Your last meal is still being digested and absorbed. Blood sugar and insulin are usually higher for a few hours after eating.[1]
- 4–12 h
Blood sugar settles
Insulin usually falls back toward its fasting level and the liver starts releasing stored glucose (glycogen) to keep blood sugar steady.[1][2]
- 12–18 h
Fat burning
As glycogen runs lower, your body is likely drawing more on stored fat, a shift researchers call the metabolic switch. It usually happens somewhere between 12 and 36 hours.[2][3][4]
- 18–24 h
Ketones rising
Your liver turns fat into ketones for fuel. Levels keep rising gradually as the fast goes on; when you reach full ketosis varies a lot from person to person.[4][2][1]
- 24 h+
Deep fast
Longer fasts are studied for effects such as autophagy. Most of that evidence comes from animal studies; results in people are still limited.[5][3]
Sources
- Cahill GF Jr. Fuel metabolism in starvation. Annu Rev Nutr 2006;26:1–22. doi
- Anton SD et al. Flipping the Metabolic Switch. Obesity 2018;26(2):254–268. doi
- de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med 2019;381:2541–2551. doi
- Johns Hopkins Medicine. Intermittent Fasting: What Is It, and How Does It Work? link
- Longo VD, Mattson MP. Fasting: molecular mechanisms and clinical applications. Cell Metab 2014;19(2):181–192. doi
Our pledge
What's free today stays free.
- The timer, your full history, widgets and every fasting schedule from 13:11 to 72h+ stay free.
- Your data is yours. Export it any time, free.
- No ads. Not in the free app, not ever.
- You can always pay once instead of subscribing.
FairFast Pro · optional, paid
More for people who want more.
Pro never takes anything away from the free app. It adds tools on top.
Plan your fasting week from a photo.
Night shifts and early shifts make a fixed 16:8 hard. Snap your roster or calendar and FairFast moves your eating window around your shifts, day by day, without making any fast longer than your goal.
Goal stays 16H · only the window moves- Meal check from a photo. Snap your first meal after a fast, get one small tip for the week. Never calories, never scores.
- Monthly report. Hours fasted, goal rate and when you fast.
- Mood and notes for each fast.
- Accent colours. Orange, blue or green.
Yearly · 7-day free trialMonthlyOnce, for life
Photos are read by Google Gemini only after you agree, and we never keep them. Subscriptions renew automatically unless cancelled at least 24 hours before the period ends; manage them in your App Store or Google Play account.
Private by design
We never see your fasting log.
No sign-up, no ads, no tracking across apps. Your fasts live on your phone, and leave it only when you export them.
AccountNone
No email, no password, no login.
Fasting logOn your phone
Fasts, schedule, notes, water and weight.
Ads & ad IDsNone
Nothing sold or shared with advertisers.
Export · deleteAny time
CSV export and delete-all, both free.
At a glance
FairFast, in plain facts.
- What it is
- An intermittent fasting tracker and fasting timer for iPhone and Android.
- Schedules
- 13:11, 14:10, 16:8, 18:6, 20:4, OMAD, and custom goals up to 168 hours.
- Free
- Timer, every schedule, daily schedule and reminders, full history, streak and stats, home and lock screen widgets, fasting stages with sources, water and weight, CSV export.
- Pro (optional)
- Plan your week from a photo, meal check from a photo, monthly report, mood and notes, accent colours. Yearly with a 7-day free trial, monthly, or once for life.
- Ads
- None.
- Account
- None needed.
- Data
- Stored on your device. The developer never sees your fasting log.
- Not for
- Anyone under 18, pregnant or breastfeeding, or with a history of eating disorders. FairFast is not a medical device.
Is FairFast free?
Yes. The fasting timer, every schedule from 13:11 to 72h+, your full history, widgets, fasting stages, water and weight tracking and CSV export are free, with no ads. FairFast Pro is optional and paid.
Do I need an account?
No. There is no sign-up and no login. Open the app, pick a schedule and start a fast.
Where is my fasting data stored?
On your phone. FairFast has no account system and no server that receives your fasts, schedule, notes, water or weight. We never see your fasting log. You can export it as CSV or delete it at any time.
Which fasting schedules does FairFast support?
13:11, 14:10, 16:8, 18:6, 20:4, OMAD, and custom goals for extended fasts up to 168 hours. Above 72 hours the app shows a note to talk to a healthcare professional.
What does FairFast Pro add?
A monthly report (hours fasted, goal rate, when you fast), mood and notes for each fast, accent colours, Plan your week from a photo, and Meal check from a photo. You can pay yearly with a 7-day free trial, monthly, or once for life.
Can I pay once instead of subscribing?
Yes. FairFast Pro is also available as a one-time purchase that you keep for life.
Does FairFast work for shift workers?
Yes. With Pro, Plan from a photo reads a photo of your shift roster or calendar and suggests a week of eating windows around your shifts, without making any fast longer than your goal.
Does the meal check count calories?
No. Meal check looks at the first meal after a fast and gives one small tip for the week. It never counts calories and never scores your food.
What breaks a fast?
Anything with calories. Water and zero-calorie drinks such as black coffee and plain tea are generally considered fine. Milk, sugar, juice and most snacks end a fast. Johns Hopkins Medicine
Which fasting schedule should I start with?
There is no single best schedule: trials comparing different ones found similar results, so choose one you can keep up. Many people start with a shorter fast such as 12:12 or 14:10 and lengthen it once that feels easy. BMJ 2025
Who should not fast without medical advice?
Do not fast if you are under 18, pregnant or breastfeeding, or have had an eating disorder. If you have diabetes, especially if you take insulin or other medicines that lower blood sugar, fasting can cause dangerously low blood sugar. If you take any regular medicine, talk to your doctor first. Mayo Clinic · Nutrients 2019
FairFast is a tracking tool. It is not a medical device and does not diagnose, treat, cure, or prevent any condition. Talk to a healthcare professional before fasting. For people aged 18 and over.
Start your next fast
the honest way.
Free on iPhone and Android. No ads, no account.
Tap to get one email when it's out. Nothing else.