# 66 Days vs Protocol66

The clearest difference is device support: 66 Days at 3 against Protocol66's 1. On price, update cadence, ads and in-app purchases there is nothing between them.

Both are free to download. 66 Days sells 5 in-app purchases, starting at $1.99 per month and Protocol66 sells 3 in-app purchases, starting at $2.99 per 7 days. Whichever you choose, the download price is not the number that matters.

66 Days ships an update every 3 weeks, Protocol66 every 2 weeks. The most recent releases landed on October 25, 2026 and October 28, 2026 respectively.

## The numbers

| Metric | 66 Days | Protocol66 |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.1 (9 ratings)](https://appshunter.io/ios/app/66-days-habit-tracker/id1439590647/reviews)** | — |
| Number of ratings | **9** | — |
| Positive reviews | 72.9% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 3 weeks | **Every 2 weeks** |
| Monetization | Freemium | — |
| Size | 19 MB | 35 MB |
| Requires iOS | 18.0 | 18.0 |
| Devices | **iPhone, iPad, Apple Watch** | iPhone |
| Age rating | 4+ | 12+ |
| Developer | [Epipherse](https://appshunter.io/developer/1231938524) | [POCKET APPS STUDIO PTE. LTD.](https://appshunter.io/developer/1864339139) |

## What reviewers say

### 66 Days

[App page](https://appshunter.io/ios/app/66-days-habit-tracker/id1439590647)

This app helps you build lasting habits by encouraging daily repetition over a 66-day period. Set project-specific goals and track your progress with features like memos, photos, and notifications.

**Highlights:** 66-day habit building system, Project-based goal setting, Daily progress tracking, Memo and photo recording, Dark mode support, Push notifications

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

**In-app purchases (5)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium 1 Month | $1.99 | per month |
| Premium 3 Month | $4.99 | per 3 months |
| Premium 1 Year | $9.99 | per year |
| Project Streak Recovery | $2.99 | one-time |
| Premium Lifetime | $22.99 | one-time |


### 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 |


## Frequently asked questions

### Is 66 Days free?

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

### Is Protocol66 free?

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

### Do 66 Days or Protocol66 have ads?

Neither 66 Days nor Protocol66 shows ads.

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

66 Days ships an update every 3 weeks, and Protocol66 every 2 weeks. Most recently, 66 Days was updated on October 25, 2026 and Protocol66 on October 28, 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.*