Sun Day Tracker vs Rays
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Sun Day Tracker
Monitor your daily vitamin D absorption from sunlight exposure. This straightforward application helps you keep track of your sun-related vitamin D intake.
- Track daily vitamin D intake
- Sunlight exposure monitoring
- Simple interface
- Daily tracking
Read full descriptionHide full description
A simple app to track you daily vitamin D intake from the sun.
Rays
Automatically tracks your body's vitamin D synthesis from sun exposure. Get personalized recommendations for optimal timing and duration to maintain energy, mood, and skin health year-round without manual logging.
- Automatic vitamin D synthesis tracking
- Personalized health intelligence
- Smart sun exposure recommendations
- Progress tracking and health insights
- Apple Health integration
- Minimal battery usage
Read full descriptionHide full description
Never Worry About Vitamin D Again Over 1 billion people are vitamin D deficient, but knowing if you’re getting enough sun shouldn’t be complicated. Rays is the world’s first app that automatically tracks your vitamin D synthesis, so you can spend your time enjoying life. No manual logging, no thinking required. Why Vitamin D Matters Optimal vitamin D levels support natural energy, balanced mood, healthy sleep cycles, and radiant skin. With Rays’ precise tracking, you can maintain these benefits year-round without guesswork or overdoing it. Automatic Vitamin D Tracking Rays uses a first-of-its-kind outdoor detection system combining GPS precision patterns, sensor data, movement analysis, and personalized machine learning that adapts to your routines. With high accuracy and minimal battery usage, it works seamlessly in the background without any manual input. Personalized Health Intelligence Our algorithm analyzes your skin type (Fitzpatrick Scale I-VI), age, geographic location, supplement intake, and lifestyle factors. Based on Endocrine Society Clinical Practice Guidelines, we provide recommendations as precise as your doctor’s, but as convenient as checking the weather. Smart Recommendations Receive personalized guidance like “Get 18 minutes at 11 AM tomorrow” based on real-time UV index, cloud cover, solar positioning, and your personal synthesis rate. Our intelligent engine suggests optimal timing when UV will be 2-3x more efficient for vitamin D production. Advanced Progress Tracking Monitor your vitamin D synthesis with detailed weekly charts, streak tracking, and comprehensive health insights. Seamlessly syncs with Apple Health and automatically adjusts for seasonal variations while preventing excessive intake when combined with supplements. For Tanners & Sun Enthusiasts Already spending time in the sun for a tan? Put that exposure to work. Rays tracks your cumulative UV dose so you can optimize your color, avoid overexposure, and know exactly where you stand — all automatically. Rays is perfect for health-conscious individuals who want optimal vitamin D without the guesswork. Try Rays free for 3 days with full access to all features. Terms of Use: https://getrays.app/eula Privacy Policy: https://getrays.app/privacy Health Disclaimer: https://getrays.app/health-disclaimer
Screenshots
Verdict
The clearest difference is in-app purchases: Sun Day Tracker at none against Rays's 2. Sun Day Tracker also leads on review sentiment (83% vs 75%) and ratings volume (26 vs 7). Rays's advantage is update cadence (every 5 days vs monthly) and iOS requirement (15.1 vs 17.0). On price, rating, ads and device support 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. Rays sells 2 in-app purchases, starting at $4.99 per month. Sun Day Tracker asks for nothing beyond the download.
Sun Day Tracker holds the better App Store score, 4.6 against 4.4. Both are backed by a comparable volume of ratings — 26 and 7 respectively. Written reviews point the same way: 83% of Sun Day Tracker's written reviews are positive against 75% of Rays's.
Sun Day Tracker ships an update monthly, Rays every 5 days. The most recent releases landed on September 19, 2026 and September 7, 2026 respectively.
| Parameter | Sun Day Tracker | Rays |
|---|---|---|
| Price | Free | Free |
| Rating | 4.6 (26 ratings) — better | 4.4 (7 ratings) |
| Positive reviews | 83.3% of reviews — better | 75.0% of reviews |
| Number of ratings | 26 — better | 7 |
| Update frequency | Monthly | Every 5 days — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Free — better | Free with in-app purchases |
| Devices | iPhone | iPhone, iPod — better |
| Requires iOS | 17.0 | 15.1 — better |
| Further details — not scored | ||
| Size | 1 MB | 58 MB |
| Age rating | 4+ | 4+ |
| Developer | permissionless tech, llc | Rays Health Technologies LLC |
Customer experience
Sun Day Tracker
Rays
In-app purchases
Sun Day Tracker
No in-app purchases
Rays
- Rays - Auto Vitamin D Tracker3 Days trial$4.991 Month
- Rays - Auto Vitamin D Tracker3 Days trial$19.991 Year









