# Four By 21 vs iSpa Spider

The clearest difference is iOS requirement: iSpa Spider at 9.0 against Four By 21's 15.6. On price, update cadence, ads and in-app purchases there is nothing between them.

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

Four By 21 ships an update every 4 months, iSpa Spider every 6 months. The most recent releases landed on October 3, 2026 and October 10, 2026 respectively.

## The numbers

| Metric | Four By 21 | iSpa Spider |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | No | No |
| Ads | Yes | Yes |
| Update frequency | **Every 4 months** | Every 6 months |
| Size | 22 MB | 22 MB |
| Requires iOS | 15.6 | **9.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Alexander Harm](https://appshunter.io/developer/1012507990) | [Manuel Lopez Lopez](https://appshunter.io/developer/1158531173) |

## What reviewers say

### Four By 21

[App page](https://appshunter.io/ios/app/four-by-21/id1501220469)

**Features:** macOS Compatibility

**In-app purchases:** none


### iSpa Spider

[App page](https://appshunter.io/ios/app/ispa-spider/id1531630683)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Four By 21 free?

Four By 21 is free to download, with no in-app purchases.

### Is iSpa Spider free?

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

### Do Four By 21 or iSpa Spider have ads?

Both Four By 21 and iSpa Spider show ads.

### Which is updated more often, Four By 21 or iSpa Spider?

Four By 21 ships an update every 4 months, and iSpa Spider every 6 months. Most recently, Four By 21 was updated on October 3, 2026 and iSpa Spider on October 10, 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.*