# Four Dimensional Space vs SkyEngine

The clearest difference is update cadence: SkyEngine at every 8 days against Four Dimensional Space's every 6 months. SkyEngine also leads on iOS requirement (17.6 vs 26.2). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Four Dimensional Space ships an update every 6 months, SkyEngine every 8 days. The most recent releases landed on October 15, 2026 and October 9, 2026 respectively.

## The numbers

| Metric | Four Dimensional Space | SkyEngine |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 6 months | **Every 8 days** |
| Size | 6 MB | 23 MB |
| Requires iOS | 26.2 | **17.6** |
| Devices | **iPhone, iPad** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Toru Kawaguchi](https://appshunter.io/developer/1063198642) | [ZIRUI LYU](https://appshunter.io/developer/1896284758) |

## What reviewers say

### Four Dimensional Space

[App page](https://appshunter.io/ios/app/four-dimensional-space/id6762447300)

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

**In-app purchases:** none


### SkyEngine

[App page](https://appshunter.io/ios/app/skyengine/id6766723696)

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

**In-app purchases:** none


## Frequently asked questions

### Is Four Dimensional Space free?

Four Dimensional Space is free to download, with no in-app purchases.

### Is SkyEngine free?

SkyEngine is free to download, with no in-app purchases.

### Do Four Dimensional Space or SkyEngine have ads?

Neither Four Dimensional Space nor SkyEngine shows ads.

### Which is updated more often, Four Dimensional Space or SkyEngine?

Four Dimensional Space ships an update every 6 months, and SkyEngine every 8 days. Most recently, Four Dimensional Space was updated on October 15, 2026 and SkyEngine on October 9, 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.*