# Marble vs Unknown app

The clearest difference is rating: Unknown app at 5.0 against Marble's 3.1. Unknown app also leads on iOS requirement (17.0 vs 26.0). Marble's advantage is in-app purchases (none vs 6) and ratings volume (8 vs 1). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Unknown app sells 6 in-app purchases, starting at $2.99 per 7 days. Marble asks for nothing beyond the download.

Unknown app holds the better App Store score, 5.0 against 3.1. That said, the two scores are not equally well evidenced: Marble has 8 ratings behind it against 1, so its average is the more settled of the two.

Both ship on a similar rhythm, roughly every 3 days. The most recent releases landed on October 31, 2026 and November 6, 2026 respectively.

## The numbers

| Metric | Marble | Unknown app |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.1 (8 ratings)](https://appshunter.io/ios/app/marble-stay-curious/id6773408198/reviews) | **[5.0 (1 ratings)](https://appshunter.io/ios/app/unknown-app/id6810123709/reviews)** |
| Number of ratings | **8** | 1 |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 3 days | Every 3 days |
| Monetization | **Free** | Freemium |
| Size | 797 MB | 58 MB |
| Requires iOS | 26.0 | **17.0** |
| Devices | iPhone, iPad | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Generative Spark Inc](https://appshunter.io/developer/1866853008) | [Vritam LP](https://appshunter.io/developer/1140400383) |

## What reviewers say

### Marble

[App page](https://appshunter.io/ios/app/marble-stay-curious/id6773408198)

An interactive world designed to spark children's curiosity into learning through exploration, quests, and problem-solving. It adapts to their interests and learning levels, offering engaging challenges and real-world activity ideas.

**Highlights:** Interactive learning worlds, Adaptive quests and challenges, Parental progress reports, Real-world activity suggestions, COPPA compliant, Designed for ages 6-12

**Features:** macOS Compatibility

**In-app purchases:** none


### Unknown app

[App page](https://appshunter.io/ios/app/unknown-app/id6810123709)

Transform dense documents into audio with a lifelike voice. Read along as text highlights in sync with narration, and even use your own voice for narration. Access your library across devices and find papers on arXiv.

**Highlights:** PDF and EPUB to audio narration, Lifelike voice narration, Customizable voice recording, Synchronized text highlighting, Cross-device syncing, arXiv paper search, Mind map generation

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

**In-app purchases (6)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unknown Pro Weekly | $2.99 | per 7 days |
| Unknown Pro Monthly | $4.99 | per month |
| Unknown Pro Yearly | $49.99 | per year |
| 3 Hours in Your Voice | $4.99 | one-time |
| 6 Hours in Your Voice | $9.99 | one-time |
| 12 Hours in Your Voice | $19.99 | one-time |


## Frequently asked questions

### Is Marble free?

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

### Is Unknown app free?

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

### Which has better reviews, Marble or Unknown app?

Unknown app is rated higher. Marble averages 3.1 out of 5 from 8 ratings, while Unknown app averages 5.0 from 1 ratings.

### Do Marble or Unknown app have ads?

Neither Marble nor Unknown app shows ads.

### Which is updated more often, Marble or Unknown app?

Marble ships an update every 3 days, and Unknown app every 3 days. Most recently, Marble was updated on October 31, 2026 and Unknown app on November 6, 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.*