Comparison

Sun Day Tracker vs Rays

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

Head to head
About

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.

Highlights
  • Track daily vitamin D intake
  • Sunlight exposure monitoring
  • Simple interface
  • Daily tracking
Features
Read full description

A simple app to track you daily vitamin D intake from the sun.

About

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.

Highlights
  • 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 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

Sun Day Tracker1 screens
Rays4 screens

Verdict

The call

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

CostPrice · In-app purchases · Ads · Monetization

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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.

Scorecard6 real differences · 4 level
Sun Day Tracker versus Rays: the parameters behind the verdict, then further details
ParameterSun Day TrackerRays
PriceFreeFree
Rating4.6 (26 ratings) — better4.4 (7 ratings)
Positive reviews83.3% of reviews — better75.0% of reviews
Number of ratings26 — better7
Update frequencyMonthlyEvery 5 days — better
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhoneiPhone, iPod — better
Requires iOS17.015.1 — better
Further details — not scored
Size1 MB58 MB
Age rating4+4+
Developerpermissionless tech, llcRays Health Technologies LLC

Customer experience

Sun Day Tracker

All ratings26 ratings
Positive88.5%
Neutral7.7%
Negative3.8%
Written reviews24 reviews
Positive83.3%
Neutral12.5%
Negative4.2%

Rays

All ratings7 ratings
Positive85.7%
Neutral0.0%
Negative14.3%
Written reviews4 reviews
Positive75.0%
Neutral0.0%
Negative25.0%

In-app purchases

None

Sun Day Tracker

No in-app purchases

2 purchases

Rays

Subscriptions2
  • Rays - Auto Vitamin D Tracker3 Days trial$4.991 Month
  • Rays - Auto Vitamin D Tracker3 Days trial$19.991 Year

Questions

Is Sun Day Tracker free?
Sun Day Tracker is free to download, with no in-app purchases.
Is Rays free?
Rays is free to download, with in-app purchases available.
Which has better reviews, Sun Day Tracker or Rays?
Sun Day Tracker is rated higher. Sun Day Tracker averages 4.6 out of 5 from 26 ratings, while Rays averages 4.4 from 7 ratings.
Do Sun Day Tracker or Rays have ads?
Neither Sun Day Tracker nor Rays shows ads.
Which is updated more often, Sun Day Tracker or Rays?
Sun Day Tracker ships an update monthly, and Rays every 5 days. Most recently, Sun Day Tracker was updated on September 19, 2026 and Rays on September 7, 2026.

Other comparisons