# Chembook vs ATC

The clearest difference is in-app purchases: ATC at none against Chembook's 1. ATC also leads on update cadence (every 5 days vs every 3 weeks). On price, ads, device support and iOS requirement there is nothing between them.

Both are free to download. Chembook sells 1 one-off in-app purchase. ATC asks for nothing beyond the download.

Chembook ships an update every 3 weeks, ATC every 5 days. The most recent releases landed on October 15, 2026 and October 29, 2026 respectively.

## The numbers

| Metric | Chembook | ATC |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 3 weeks | **Every 5 days** |
| Size | 110 MB | 63 MB |
| Requires iOS | 17.0 | **16.4** |
| Devices | iPhone, iPad | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Hyuk-Yong Kwon](https://appshunter.io/developer/6796681340) | [ThinkonWeb Inc.](https://appshunter.io/developer/1813804936) |

## What reviewers say

### Chembook

[App page](https://appshunter.io/ios/app/chembook-reaction-visualizer/id6796681338)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro | $6.99 | one-time |


### ATC

[App page](https://appshunter.io/ios/app/atc-18/id6814372909)

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

**In-app purchases:** none


## Frequently asked questions

### Is Chembook free?

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

### Is ATC free?

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

### Do Chembook or ATC have ads?

Neither Chembook nor ATC shows ads.

### Which is updated more often, Chembook or ATC?

Chembook ships an update every 3 weeks, and ATC every 5 days. Most recently, Chembook was updated on October 15, 2026 and ATC on October 29, 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.*