# Crystal Me vs Quantum Mechanics Notes

The clearest difference is update cadence: Quantum Mechanics Notes at daily against Crystal Me's every 5 days. Crystal Me's advantage is iOS requirement (15.0 vs 17.0). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Crystal Me sells 1 one-off in-app purchase and Quantum Mechanics Notes sells 4 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.

Crystal Me ships an update every 5 days, Quantum Mechanics Notes daily. The most recent releases landed on October 11, 2026 and October 3, 2026 respectively.

## The numbers

| Metric | Crystal Me | Quantum Mechanics Notes |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 5 days | **Daily** |
| Size | 159 MB | 32 MB |
| Requires iOS | **15.0** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [梦琦 徐](https://appshunter.io/developer/1784852515) | [际 郭](https://appshunter.io/developer/6797282134) |

## What reviewers say

### Crystal Me

[App page](https://appshunter.io/ios/app/crystal-me/id6741855152)

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 水晶Crystal Pro | $0.99 | one-time |


### Quantum Mechanics Notes

[App page](https://appshunter.io/ios/app/quantum-mechanics-notes/id6808079339)

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 支持作者 ¥6 | $0.99 | one-time |
| 支持作者 ¥1 | $0.99 | one-time |
| 支持作者 ¥8 | $0.99 | one-time |
| 支持作者 ¥28 | $3.99 | one-time |


## Frequently asked questions

### Is Crystal Me free?

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

### Is Quantum Mechanics Notes free?

Quantum Mechanics Notes is free to download, with in-app purchases available.

### Do Crystal Me or Quantum Mechanics Notes have ads?

Neither Crystal Me nor Quantum Mechanics Notes shows ads.

### Which is updated more often, Crystal Me or Quantum Mechanics Notes?

Crystal Me ships an update every 5 days, and Quantum Mechanics Notes daily. Most recently, Crystal Me was updated on October 11, 2026 and Quantum Mechanics Notes on October 3, 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.*