# Protocol66 vs 66 Challenge

The clearest difference is update cadence: 66 Challenge at every 5 days against Protocol66's every 2 weeks. 66 Challenge also leads on device support (3 vs 1) and iOS requirement (13.0 vs 18.0). On price, ads and in-app purchases there is nothing between them.

Both are free to download. Protocol66 sells 3 in-app purchases, starting at $2.99 per 7 days and 66 Challenge sells 3 in-app purchases, starting at $3.99 per month. Whichever you choose, the download price is not the number that matters.

Protocol66 ships an update every 2 weeks, 66 Challenge every 5 days. The most recent releases landed on October 6, 2026 and October 5, 2026 respectively.

## The numbers

| Metric | Protocol66 | 66 Challenge |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (5 ratings)](https://appshunter.io/ios/app/66-challenge/id6758270405/reviews)** |
| Number of ratings | — | **5** |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 2 weeks | **Every 5 days** |
| Monetization | — | Freemium |
| Size | 35 MB | 18 MB |
| Requires iOS | 18.0 | **13.0** |
| Devices | iPhone | **iPhone, iPad, iPod** |
| Age rating | 12+ | 12+ |
| Developer | [POCKET APPS STUDIO PTE. LTD.](https://appshunter.io/developer/1864339139) | [Moad Ghajjate El Fal](https://appshunter.io/developer/1871890791) |

## What reviewers say

### Protocol66

[App page](https://appshunter.io/ios/app/protocol66/id6757076988)

**Features:** macOS Compatibility

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Version | $2.99 | per 7 days |
| Pro | $19.99 | per year |
| Lifetime Access | $3.99 | one-time |


### 66 Challenge

[App page](https://appshunter.io/ios/app/66-challenge/id6758270405)

Build lasting habits with a science-backed system designed to guide you through a 66-day journey. Track daily progress, visualize your transformation, and stay motivated with social features and achievements. Transform your life one habit at a time.

**Highlights:** Daily habit tracking, Progress visualization, Streak protection, Social feed and squads, Customizable reminders, Achievement badges

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Monthly | $3.99 | per month |
| Pro Annual | $29.99 | per year |
| Pro Lifetime | $59.99 | one-time |


## Frequently asked questions

### Is Protocol66 free?

Protocol66 is free to download, with in-app purchases available.

### Is 66 Challenge free?

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

### Do Protocol66 or 66 Challenge have ads?

Neither Protocol66 nor 66 Challenge shows ads.

### Which is updated more often, Protocol66 or 66 Challenge?

Protocol66 ships an update every 2 weeks, and 66 Challenge every 5 days. Most recently, Protocol66 was updated on October 6, 2026 and 66 Challenge on October 5, 2026.

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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.*