# String GOAT vs ChallengeBu!

The clearest difference is in-app purchases: ChallengeBu! at none against String GOAT's 5. ChallengeBu! also leads on ads (none vs shown). On price, update cadence, device support and iOS requirement there is nothing between them.

Both are free to download. String GOAT sells 5 in-app purchases, starting at $4.99 per month. ChallengeBu! asks for nothing beyond the download.

Both ship on a similar rhythm, roughly every 3 days. The most recent releases landed on October 27, 2026 and October 16, 2026 respectively.

## The numbers

| Metric | String GOAT | ChallengeBu! |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.8 (9 ratings)](https://appshunter.io/ios/app/string-goat-for-tennis/id6444395925/reviews)** | — |
| Number of ratings | **9** | — |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | Yes | **No** |
| Update frequency | Every 3 days | Every 3 days |
| Monetization | Free with in-app purchases | — |
| Size | 116 MB | 38 MB |
| Requires iOS | **16.1** | 16.4 |
| Devices | **iPhone, Apple Watch** | iPhone |
| Age rating | 4+ | 12+ |
| Developer | [YOSEOP YOON](https://appshunter.io/developer/1654444723) | [Hazar Ustun](https://appshunter.io/developer/1885352713) |

## What reviewers say

### String GOAT

[App page](https://appshunter.io/ios/app/string-goat-for-tennis/id6444395925)

Track your tennis string performance and racket setups. Log detailed specs, rate performance across key categories with radar charts, and get AI-powered recommendations for optimal string choices and tension.

**Highlights:** Racket and string setup logging, Performance rating with radar charts, Tension history analysis, AI-powered string recommendations, Cloud sync and backup, Home screen widget

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

**In-app purchases (5)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Monthly | $4.99 | per month |
| Premium Monthly | $9.99 | per month |
| Pro Yearly | $41.99 | per year |
| Premium Yearly | $83.99 | per year |
| String GOAT Premium Service | $9.99 | one-time |


### ChallengeBu!

[App page](https://appshunter.io/ios/app/challengebu/id6785916807)

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

**In-app purchases:** none


## Frequently asked questions

### Is String GOAT free?

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

### Is ChallengeBu! free?

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

### Do String GOAT or ChallengeBu! have ads?

String GOAT shows ads; ChallengeBu! does not.

### Which is updated more often, String GOAT or ChallengeBu!?

String GOAT ships an update every 3 days, and ChallengeBu! every 3 days. Most recently, String GOAT was updated on October 27, 2026 and ChallengeBu! on October 16, 2026.

---

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