# Castle Siege TD vs Backpack Tower Defense

The clearest difference is in-app purchases: Castle Siege TD at none against Backpack Tower Defense's 8. Castle Siege TD also leads on iOS requirement (11.0 vs 15.0). Backpack Tower Defense's advantage is update cadence (weekly vs every 3 weeks). On price and device support there is nothing between them.

Both are free to download. Backpack Tower Defense sells 8 one-off in-app purchases. Castle Siege TD asks for nothing beyond the download.

Castle Siege TD ships an update every 3 weeks, Backpack Tower Defense weekly. The most recent releases landed on October 27, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | Castle Siege TD | Backpack Tower Defense |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[1.0 (1 ratings)](https://appshunter.io/ios/app/backpack-tower-defense/id6762122942/reviews)** |
| Number of ratings | — | **1** |
| In-app purchases | **No** | Yes |
| Ads | — | Yes |
| Update frequency | Every 3 weeks | **Weekly** |
| Monetization | — | Free with in-app purchases |
| Size | 111 MB | 175 MB |
| Requires iOS | **11.0** | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Eric Unterberger](https://appshunter.io/developer/1667139892) | [Ngo Nguyen](https://appshunter.io/developer/1833419289) |

## What reviewers say

### Castle Siege TD

[App page](https://appshunter.io/ios/app/castle-siege-td/id1662056250)

**In-app purchases:** none


### Backpack Tower Defense

[App page](https://appshunter.io/ios/app/backpack-tower-defense/id6762122942)

A strategic game where organizing your backpack is key to defending against monster waves. Merge heroes and weapons to create powerful combinations and defeat bosses in fast-paced battles.

**Highlights:** Innovative backpack management, Tower defense strategy, Merge heroes and weapons, Epic boss fights, Roguelike builds, Idle RPG progression

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

**In-app purchases (8)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Spark Gems | $1.99 | one-time |
| Boost Gems | $3.99 | one-time |
| Remove ads | $4.99 | one-time |
| Starter Pack | $4.99 | one-time |
| Power Gems | $7.99 | one-time |
| Elite Gems | $17.99 | one-time |
| Master Gems | $34.99 | one-time |
| Infinity Gems | $79.99 | one-time |


## Frequently asked questions

### Is Castle Siege TD free?

Castle Siege TD is free to download, with no in-app purchases.

### Is Backpack Tower Defense free?

Backpack Tower Defense is free to download, with in-app purchases available.

### Which is updated more often, Castle Siege TD or Backpack Tower Defense?

Castle Siege TD ships an update every 3 weeks, and Backpack Tower Defense weekly. Most recently, Castle Siege TD was updated on October 27, 2026 and Backpack Tower Defense on October 25, 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.*