# Circadian Rhythm vs FastWindow

The clearest difference is iOS requirement: FastWindow at 15.1 against Circadian Rhythm's 17.0. On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Circadian Rhythm sells 3 in-app purchases, starting at $4.99 per month and FastWindow sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

## The numbers

| Metric | Circadian Rhythm | FastWindow |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.6 (11 ratings)](https://appshunter.io/ios/app/circadian-rhythm-body-clock/id6737418117/reviews)** | — |
| Number of ratings | **11** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Monthly | — |
| Monetization | Free with in-app purchases | — |
| Size | 18 MB | 37 MB |
| Requires iOS | 17.0 | **15.1** |
| Devices | **iPhone, iPad, Apple Watch** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Joaquin Marticorena](https://appshunter.io/developer/1774135480) | [PROJECTSNAPLABS LTD](https://appshunter.io/developer/1889904681) |

## What reviewers say

### Circadian Rhythm

[App page](https://appshunter.io/ios/app/circadian-rhythm-body-clock/id6737418117)

Align your daily routines with your body's natural biological clock. Gain personalized insights to improve sleep, boost energy, and enhance focus by understanding your circadian rhythm. Optimize your day with alerts for hormone peaks and sunlight guidance.

**Highlights:** Circadian Rhythm Tracking, Sleep Insights & Trends, Hormone Peak Information, Daily Rhythm Alerts, Mood Tracking, Sunlight Guidance, Personalized Recommendations

**Features:** macOS Compatibility, Apple Watch app, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Circadian PRO | $4.99 | per month |
| Circadian PRO | $29.99 | per year |
| Lifetime Premium | $4.99 | one-time |


### FastWindow

[App page](https://appshunter.io/ios/app/fastwindow-fasting-timer/id6764386746)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| FastWindow Pro | $4.99 | one-time |


## Frequently asked questions

### Is Circadian Rhythm free?

Circadian Rhythm is free to download, with in-app purchases available.

### Is FastWindow free?

FastWindow is free to download, with in-app purchases available.

### Do Circadian Rhythm or FastWindow have ads?

Neither Circadian Rhythm nor FastWindow shows ads.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*