# Knock, knock, knock! vs Shelf

The clearest difference is price: Shelf at Free against Knock, knock, knock!'s $2.99. Shelf also leads on update cadence (every 5 weeks vs every 48 months). Knock, knock, knock!'s advantage is iOS requirement (9.3 vs 15.0). On ads, in-app purchases and device support there is nothing between them.

Shelf is free to download; Knock, knock, knock! costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Knock, knock, knock! ships an update every 48 months, Shelf every 5 weeks. The most recent releases landed on October 24, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | Knock, knock, knock! | Shelf |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | — | **[4.7 (7 ratings)](https://appshunter.io/ios/app/shelf/id1620828408/reviews)** |
| Number of ratings | — | **7** |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 48 months | **Every 5 weeks** |
| Monetization | Paid | **Ad-supported** |
| Size | 121 MB | 40 MB |
| Requires iOS | **9.3** | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 12+ |
| Developer | [Alfabeta](https://appshunter.io/developer/586381859) | [Beat Technology AS](https://appshunter.io/developer/433400941) |

## What reviewers say

### Knock, knock, knock!

[App page](https://appshunter.io/ios/app/knock-knock-knock/id586381856)

This interactive book app brings a classic children's story to life with engaging page-turning and the ability to record your own narration. It's designed for young children to enjoy a beloved tale in a new digital format.

**Highlights:** Interactive page turning, Recordable narration, Multiple language options, Classic children's story, Designed for toddlers

**In-app purchases:** none


### Shelf

[App page](https://appshunter.io/ios/app/shelf/id1620828408)

Access your personal library of purchased audiobooks and e-books. Read or listen anywhere, anytime, with or without an internet connection. Enjoy your collection without subscriptions or time limits.

**Highlights:** Access purchased audiobooks and e-books, Read or listen offline, No subscriptions or time limits, Bookmark and comment, Customize reading experience, Adjust playback speed, Sleep timer for audiobooks

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Knock, knock, knock! free?

Knock, knock, knock! costs $2.99, with no in-app purchases.

### Is Shelf free?

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

### Do Knock, knock, knock! or Shelf have ads?

Neither Knock, knock, knock! nor Shelf shows ads.

### Which is updated more often, Knock, knock, knock! or Shelf?

Knock, knock, knock! ships an update every 48 months, and Shelf every 5 weeks. Most recently, Knock, knock, knock! was updated on October 24, 2026 and Shelf 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.*