SOL vs CoreFast
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
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.
CoreFast
This app helps you track intermittent fasting with customizable plans and a live timer. It offers optional food and water logging, and can integrate with health data. Features include reminders, streaks, and social challenges, all while prioritizing user privacy.
- Customizable intermittent fasting plans
- Live accurate timer
- Optional food and water logging
- Apple Health integration for readings
- Privacy-focused, data stays on device
- Widgets and Apple Watch app support
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CoreFast is a calm intermittent fasting tracker that keeps your data on your phone. Pick a plan, tap Start, and see where your fast is at a glance. No account. No ads. No surprise charges. Ending a fast early is recorded neutrally, never as a failure. Today and plans • A live timer that stays accurate if you close the app or go offline • Daily plans from 12:12 to 23:1, plus 5:2, alternate-day, Sunrise to sunset and a custom plan • Each plan explains what a day on it looks like before you switch • Water tracking with your own daily goal • Optional local reminders, with quiet hours • Optional streaks with a weekly rest day, and challenges you choose to join • Longer fasts come with a short sheet on what to expect and when to stop Food log (optional) • Log what you eat during your eating window • Scan packaged foods by barcode (you can turn this off in Settings) • See calories that other apps log to Apple Health Health readings (optional) Connect Apple Health to see last night's sleep, steps, active calories, resting heart rate, HRV and glucose next to your fast. CoreFast only reads; it never writes to Apple Health. Vitals shows your readings over 7 days, 30 days or all time, compared only with your own usual range, and a summary you can share if you choose. Readings are shown as recorded, not as an assessment. Insights and Learn Trends, history and a month calendar show how your fasts have gone. Week on week compares you only with yourself. Learn has 18 short reads in plain language, each with a link to its source. New to fasting? For your first four weeks, Today shows one short tip a day. Circles (optional) Fast alongside a few friends. Share your status, send a cheer, or run a group challenge, like Sugar free or a water goal, with a shared leaderboard. Updates are encrypted and pass through a relay that keeps them for up to 24 hours. Your fasting history and health readings are never sent. Widgets, Watch and Siri • Home Screen, Lock Screen and StandBy widgets; fast details stay hidden while your iPhone is locked • A Live Activity and Dynamic Island countdown • An Apple Watch app with one-tap End and Undo • Siri, Shortcuts, and Controls for Control Center, the Lock Screen and the Action button Private by design Your fasts, food log, water and health readings stay on your device, stored encrypted. They are never sent to us or to any server. If you turn on barcode scanning, only the barcode number is looked up, at Open Food Facts. No account, no ads, no third-party analytics or tracking. Your location is used only if you choose the Sunrise to sunset plan, and is kept on your phone. Export a backup or spreadsheet whenever you like, or delete everything from Settings. A note on safety CoreFast is a tracking tool for general wellness. It is not a medical device and does not give medical advice. Fasting isn't right for everyone: talk to your clinician before you start, especially if you are pregnant, take medicines for diabetes, or have a history of disordered eating. Stop and eat if you feel unwell. A few private questions at the start can switch CoreFast to simple time logging, a quieter app with no streaks or longer plans. Questions or feedback: corefast.support@icloud.com
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Verdict
The clearest difference is in-app purchases: CoreFast at none against SOL's 3. CoreFast also leads on update cadence (daily 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
Both are free to download. SOL sells 3 one-off in-app purchases. CoreFast asks for nothing beyond the download.
SOL ships an update fortnightly, CoreFast daily. The most recent releases landed on October 24, 2026 and October 29, 2026 respectively.
| Parameter | SOL | CoreFast |
|---|---|---|
| Price | Free | Free |
| Rating | — | 5.0 (4 ratings) — better |
| Positive reviews | — | 100.0% of reviews |
| Number of ratings | — | 4 — better |
| Update frequency | Fortnightly | Daily — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | — | Free |
| Devices | iPhone, iPod | iPhone, iPad, Apple Watch — better |
| Requires iOS | 16 — better | 16.4 |
| Further details — not scored | ||
| Size | 7 MB | 55 MB |
| Age rating | 4+ | 17+ |
| Developer | Danny Linsner | SATISH CHANDRA KOLLI |
In-app purchases
SOL
- Seedling Tip$1.99
- Sapling Tip$3.99
- Pine Tip$8.99
CoreFast
No in-app purchases









