# Defend the Brain vs Protocol 4

The clearest difference is ads: Defend the Brain at none against Protocol 4's shown. Defend the Brain also leads on update cadence (every 5 weeks vs every 3 months) and iOS requirement (8.0 vs 17.0). On price, in-app purchases and device support there is nothing between them.

Both are free to download. Defend the Brain sells 1 one-off in-app purchase and Protocol 4 sells 7 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.

Defend the Brain ships an update every 5 weeks, Protocol 4 every 3 months. Both last shipped on October 8, 2026.

## The numbers

| Metric | Defend the Brain | Protocol 4 |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (2 ratings)](https://appshunter.io/ios/app/defend-the-brain-right-left-brain-test/id1240222889/reviews)** | — |
| Number of ratings | **2** | — |
| In-app purchases | Yes | Yes |
| Ads | **No** | Yes |
| Update frequency | **Every 5 weeks** | Every 3 months |
| Monetization | Free with in-app purchases | — |
| Size | 57 MB | 12 MB |
| Requires iOS | **8.0** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 9+ | 4+ |
| Developer | [Pixel Bistro](https://appshunter.io/developer/976506039) | [HAKAN OZGER](https://appshunter.io/developer/1855495033) |

## What reviewers say

### Defend the Brain

[App page](https://appshunter.io/ios/app/defend-the-brain-right-left-brain-test/id1240222889)

Test your brain's speed and dominance between the left and right hemispheres. Compete globally in a game of split-second reactions. See if you can keep up with historical geniuses.

**Highlights:** Brain speed test, Left vs. Right brain dominance, Global leaderboards, Split-second reaction challenges, Compete with friends

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Remove Ads | $0.99 | one-time |


### Protocol 4

[App page](https://appshunter.io/ios/app/protocol-4-code-breaker-pvp/id6755742805)

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

**In-app purchases (7)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pocket Change | $0.99 | one-time |
| Starter Kit | $1.99 | one-time |
| Agent License | $2.99 | one-time |
| Hacker's Stash | $4.99 | one-time |
| Pro Kit | $4.99 | one-time |
| Trust Fund | $9.99 | one-time |
| Master Kit | $9.99 | one-time |


## Frequently asked questions

### Is Defend the Brain free?

Defend the Brain is free to download, with in-app purchases available.

### Is Protocol 4 free?

Protocol 4 is free to download, with in-app purchases available.

### Do Defend the Brain or Protocol 4 have ads?

Protocol 4 shows ads; Defend the Brain does not.

### Which is updated more often, Defend the Brain or Protocol 4?

Defend the Brain ships an update every 5 weeks, and Protocol 4 every 3 months. Most recently, Defend the Brain was updated on October 8, 2026 and Protocol 4 on October 8, 2026.

---

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