Comparison

Fast.io vs Sundial

Price, ratings, monetisation and update history for both apps, side by side β€” with what reviewers say about each.

Head to head
About

Fast.io

Features
Read full description

Fast.io is a beautifully simple intermittent fasting timer designed to help you stay consistent and focused on your fasting goals. Track your fast in real time, monitor hydration, and stay motivated with clear insights, widgets, and Live Activities. Perfect for popular fasting schedules like **16:8, 18:6, or OMAD**. #### TRACK YOUR FAST β€’ Start fasting sessions with presets like 16:8, 18:6, or create custom fasting intervals β€’ See elapsed time, remaining time, and fasting phases\ β€’ Follow your fasting progress in real time #### TRACK YOUR WEIGHT β€’ Sync weight with Apple Health β€’ Monitor weight changes during fasting β€’ Understand how fasting affects your body #### STAY CONSISTENT β€’ Local reminders for fasting milestones β€’ Daily hydration tracking β€’ Motivation through achievements and streaks #### SEE YOUR PROGRESS β€’ History with notes and mood tracking β€’ Weekly, monthly, and yearly statistics β€’ Understand and improve your fasting habits #### BUILT FOR APPLE DEVICES β€’ Live Activities and Dynamic Island β€’ Home Screen and Lock Screen widgets β€’ Apple Watch companion app #### PRO FEATURES β€’ One‑time purchase (no subscription) β€’ Advanced customization β€’ Extended fasting history Fast.io is designed to make intermittent fasting simple, beautiful, and effective.

About

Sundial

Features
Read full description

Finally, a fasting timer you buy once and own for life. No subscription. No account. No quiz-funnel paywall. Just open it and start your fast. Sundial is a calm, local-first tracker for intermittent fasting and OMAD (one meal a day). One quiet ring; a sun crosses the dial as your fast deepens. Warm paper-and-ember design, automatic dark mode. No neon, no confetti, no streak-shaming. It works fully offline from the very first tap. WHY SUNDIAL IS DIFFERENT - Pay once, $19.99. No $60-80/year renewals for a glorified timer. - No forced sign-up, no quiz funnel, no data siphoning. Cloud backup is optional, never required. - Fasting zones and stages are explained for free - learn what each stage is called, hour by hour. Most apps lock this away. - Custom durations up to 72 hours - log any fast you choose, with no upsell. - Retroactive editing: forgot to hit start or stop? Fix it, or log a past fast. - Your eating window anchors to when you actually broke the fast - not a rigid schedule. FREE FOREVER - Timer for every protocol: 16:8, 18:6, 20:4, OMAD, 36h, and custom. - Fasting zones and stage labels on the dial. - History, calendar, streaks, and weekly stats. - Weight, water, and mood logging. - Gentle notifications for start, end, and milestones. - Export everything to CSV or JSON in two taps. Your data is yours. LIFETIME UNLOCK ($19.99, ONCE) - Cloud backup and cross-device sync. - Insights: deeper trends over time. - The full Field Notes library of calm, readable articles - including a plain explainer of what autophagy is. Everything you need to fast is already free. Lifetime is for going further, on your terms. BUILT TO RESPECT YOU Local-first and private by design. No ads, no data mining, no guilt loops, no upsell screens between you and your timer. A quieter way to keep time. Sundial tracks time. It is not medical advice. Talk to a healthcare professional before changing how you eat or starting extended fasts, especially if you are under 18, pregnant, managing diabetes, or have a history of disordered eating.

Screenshots

Fast.io4 screens
Sundial4 screens

Verdict

The call

The clearest difference is iOS requirement: Sundial at 16.4 against Fast.io's 26.0. On price, ads, in-app purchases and device support there is nothing between them.

Scored on Price Β· Rating Β· Positive reviews Β· Number of ratings Β· Update frequency Β· Ads Β· In-app purchases Β· Monetization Β· Best chart rank Β· Devices Β· Requires iOS

CostPrice Β· In-app purchases Β· Ads Β· Monetization

Both are free to download. Fast.io sells 1 one-off in-app purchase and Sundial sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Scorecard1 real difference Β· 5 level
Fast.io versus Sundial: the parameters behind the verdict, then further details
ParameterFast.ioSundial
PriceFreeFree
Update frequencyMonthlyβ€”
AdsNoNo
In-app purchasesYesYes
DevicesiPhone, Apple Watch β€” betteriPhone
Requires iOS26.016.4 β€” better
Further details β€” not scored
Size23 MB65 MB
Age rating4+4+
DeveloperStefan SturmVitalii Iudin

In-app purchases

1 purchases

Fast.io

One-time1
  • Fast.io Pro$6.99
1 purchases

Sundial

One-time1
  • Sundial Lifetime$19.99

Questions

Is Fast.io free?
Fast.io is free to download, with in-app purchases available.
Is Sundial free?
Sundial is free to download, with in-app purchases available.
Do Fast.io or Sundial have ads?
Neither Fast.io nor Sundial shows ads.

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