# Graycode vs 开心听书

The clearest difference is review sentiment: Graycode at 67% against 开心听书's 0%. Graycode also leads on in-app purchases (none vs 4). 开心听书's advantage is price (Free vs $2.99) and update cadence (every 2 weeks vs every 10 months). On ads, device support and iOS requirement there is nothing between them.

开心听书 is free to download; Graycode costs $2.99 up front. 开心听书 sells 4 in-app purchases, starting at $0.49 per month. Graycode asks for nothing beyond the download.

Graycode ships an update every 10 months, 开心听书 every 2 weeks. The most recent releases landed on October 11, 2026 and September 30, 2026 respectively.

## The numbers

| Metric | Graycode | 开心听书 |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | **[3.0 (2 ratings)](https://appshunter.io/ios/app/graycode/id548428653/reviews)** | — |
| Number of ratings | **2** | — |
| Positive reviews | **66.7% of reviews** | 0.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 10 months | **Every 2 weeks** |
| Monetization | Paid | **Freemium** |
| Size | 2 MB | 12 MB |
| Requires iOS | **12.0** | 13.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Duo Pisceses, Inc.](https://appshunter.io/developer/850707063) | [滨亮 马](https://appshunter.io/developer/1534089950) |

## What reviewers say

### Graycode

[App page](https://appshunter.io/ios/app/graycode/id548428653)

This utility converts numbers between decimal, hexadecimal, binary, and Gray code formats. Changes to one value automatically update the others, making it a convenient tool for engineers. It also features an animated demonstration of the Tower of Hanoi puzzle.

**Highlights:** Decimal, hex, binary, Gray code conversion, Real-time updates, Handy calculator for engineers, Animated Tower of Hanoi solution, Supports iPhone, iPad, iPod

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

**In-app purchases:** none


### 开心听书

[App page](https://appshunter.io/ios/app/id1569205986)

Listen to a wide variety of books daily, including classics, educational content, and popular series. Offers daily updates and various subscription options for unlimited access.

**Highlights:** Daily audiobook listening, Extensive book library, Daily updates, Subscription plans, Parental education content

**Features:** macOS Compatibility

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 超级会员连续包月 | $0.49 | per month |
| 超级会员连续包年 | $1.99 | per year |
| 超级会员连续包周 | $5.49 | per 7 days |
| 超级永久会员 | $4.99 | one-time |


## Frequently asked questions

### Is Graycode free?

Graycode costs $2.99, with no in-app purchases.

### Is 开心听书 free?

开心听书 is free to download, with in-app purchases available.

### Do Graycode or 开心听书 have ads?

Neither Graycode nor 开心听书 shows ads.

### Which is updated more often, Graycode or 开心听书?

Graycode ships an update every 10 months, and 开心听书 every 2 weeks. Most recently, Graycode was updated on October 11, 2026 and 开心听书 on September 30, 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.*