Comparison

SOL vs The Fast

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

Head to head
About

SOL

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SOL (솔) is Korean for pine tree. Like the pine that endures through every season, SOL stands with you through every fast. WHAT MAKES SOL DIFFERENT Most fasting apps just show a timer. SOL shows you what is happening inside your body as the hours pass, with the research behind it. As you fast, SOL guides you through eight phases: Fed State, Insulin Dropping, Fat Burning, Ketosis, Autophagy, Deep Autophagy, Growth Hormone Surge and Immune Reset. FEATURES • A calm timer with a progress ring and phase markers • Your fast on the lock screen and in the Dynamic Island • All 8 phases explained, with links to the published studies • A goal dial from 12 to 72 hours, or an open fast with no limit • Started earlier? Set the time you last ate, and correct it later • Switch the timer between time elapsed and time to go • A daily reminder to start your fast • Your Journey: stats, streaks, a 7 day view and your history • Edit, add or delete past fasts • Guidance on breaking your fast gently • Home screen widget • "Start my fast" with Siri • Share your results with a beautiful card • Light and dark mode with handcrafted watercolor textures FASTING TOGETHER If you like, join the live count of people fasting right now. It is optional, anonymous and off until you turn it on. YOUR DATA No account, no ads, no tracking. Your fasting data stays on your device unless you choose to join the community count or turn on iCloud backup. DESIGNED WITH INTENTION SOL is inspired by the simplicity of nature. No clutter and no paywall. Just you, your fast, and a clearer picture of what your body is doing. SOL is free. If you enjoy it, you can leave a tip. ABOUT THE SCIENCE Phase information is based on peer-reviewed research, with direct links to the sources. Some findings come from animal studies, and every body responds differently. SOL offers general wellness information and is not medical advice. Please talk to a doctor before fasting, especially for longer fasts. Begin your fast. Know your body. Grow like the pine.

About

The Fast

Track your fasting periods with a visual timer and home screen widgets. Review your history in a calendar and share your progress as an image. Use the app without an account for local data storage, or sign in to sync across devices.

Highlights
  • Visual fasting timer
  • Home screen widgets
  • Fasting history calendar
  • Shareable progress images
  • Account-free operation
  • Cross-device sync
Features
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Fasting, at your pace. Choose a duration and start. A slowly moving record marks the time, with elapsed time and time remaining always within reach. ON YOUR HOME SCREEN Small and medium widgets keep your fast in view. See elapsed time at a glance, or use the larger widget for the full record, progress and time remaining. A MONTH, ON RECORD Browse your fasting history in a simple calendar. Finished goals retain their record color. Early endings appear in gray. Open any day to see each fast. YOURS TO SHARE Share one fast or your whole month as a single image. Include record details and exact times when you want to. LIGHT BY DESIGN Use the timer, history and widgets without an account. Your records stay on your device unless you choose to sync them. Optional Apple, Google or email sign-in lets you keep records across devices. Free to use. No ads. The Fast records time. It does not provide medical or dietary advice.

Screenshots

SOL4 screens
The Fast4 screens

Verdict

The call

The clearest difference is in-app purchases: The Fast at none against SOL's 3. The Fast also leads on update cadence (every 3 days vs fortnightly). On price, ads, device support and iOS requirement there is nothing between them.

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

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. SOL sells 3 one-off in-app purchases. The Fast asks for nothing beyond the download.

UpkeepUpdate frequency

SOL ships an update fortnightly, The Fast every 3 days. The most recent releases landed on October 24, 2026 and October 29, 2026 respectively.

Scorecard2 real differences · 7 level
SOL versus The Fast: the parameters behind the verdict, then further details
ParameterSOLThe Fast
PriceFreeFree
Rating—5.0 (3 ratings) — better
Number of ratings—3 — better
Update frequencyFortnightlyEvery 3 days — better
AdsNoNo
In-app purchasesYesNo — better
Monetization—Free
DevicesiPhone, iPod — betteriPhone
Requires iOS16 — better16.4
Further details — not scored
Size7 MB31 MB
Age rating4+4+
DeveloperDanny LinsnerPrime Adventure LLC

In-app purchases

3 purchases

SOL

One-time3
  • Seedling Tip$1.99
  • Sapling Tip$3.99
  • Pine Tip$8.99
None

The Fast

No in-app purchases

Questions

Is SOL free?
SOL is free to download, with in-app purchases available.
Is The Fast free?
The Fast is free to download, with no in-app purchases.
Do SOL or The Fast have ads?
Neither SOL nor The Fast shows ads.
Which is updated more often, SOL or The Fast?
SOL ships an update fortnightly, and The Fast every 3 days. Most recently, SOL was updated on October 24, 2026 and The Fast on October 29, 2026.

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