# YKI Test vs Sum Serenity

The clearest difference is update cadence: YKI Test at every 2 days against Sum Serenity's every 8 months. On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. YKI Test sells 1 one-off in-app purchase and Sum Serenity sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

YKI Test ships an update every 2 days, Sum Serenity every 8 months. Both last shipped on October 24, 2026.

## The numbers

| Metric | YKI Test | Sum Serenity |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | **Every 2 days** | Every 8 months |
| Size | 28 MB | 28 MB |
| Requires iOS | 15.1 | **15.0** |
| Devices | iPhone, iPod | iPhone, iPod |
| Age rating | 9+ | 4+ |
| Developer | [Shamnad Padinjarechalil Shaji](https://appshunter.io/developer/1711058538) | [Blossom Labs Ltd](https://appshunter.io/developer/1723890403) |

## What reviewers say

### YKI Test

[App page](https://appshunter.io/ios/app/yki-test/id6468961028)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Remove Ads | $0.99 | one-time |


### Sum Serenity

[App page](https://appshunter.io/ios/app/sum-serenity-mental-maths/id6475314608)

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Serenity Seeker | $1.99 | one-time |


## Frequently asked questions

### Is YKI Test free?

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

### Is Sum Serenity free?

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

### Do YKI Test or Sum Serenity have ads?

Neither YKI Test nor Sum Serenity shows ads.

### Which is updated more often, YKI Test or Sum Serenity?

YKI Test ships an update every 2 days, and Sum Serenity every 8 months. Most recently, YKI Test was updated on October 24, 2026 and Sum Serenity on October 24, 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.*