# KKUK vs Sumbi

The clearest difference is ads: Sumbi at none against KKUK's shown. Sumbi also leads on monetization model (free vs free with in-app purchases) and iOS requirement (16.4 vs 18.0). On price, review sentiment, update cadence and in-app purchases there is nothing between them.

Both are free to download. KKUK sells 2 in-app purchases, starting at $1.99 per month and Sumbi sells 3 one-off in-app purchases. Whichever you choose, the download price is not the number that matters.

KKUK ships an update every 5 days, Sumbi weekly. Both last shipped on October 31, 2026.

## The numbers

| Metric | KKUK | Sumbi |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (1 ratings)](https://appshunter.io/ios/app/sumbi-study-focus-timer/id6802502926/reviews)** |
| Number of ratings | — | **1** |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| In-app purchases | Yes | Yes |
| Ads | Yes | **No** |
| Update frequency | **Every 5 days** | Weekly |
| Monetization | Free with in-app purchases | **Free** |
| Size | 82 MB | 94 MB |
| Requires iOS | 18.0 | **16.4** |
| Devices | **iPhone, Apple Watch** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Sangcheol Kim](https://appshunter.io/developer/6786085612) | [나이스데이](https://appshunter.io/developer/1751418356) |

## What reviewers say

### KKUK

[App page](https://appshunter.io/ios/app/kkuk-lock-screen-habits/id6797384948)

Track your habits by stamping them on a calendar. This app allows you to create custom stamps with colors and emojis, and view your progress through various reports. It offers lock screen and widget integration for easy access.

**Highlights:** Stamp habits on a calendar, Customizable stamps with colors and emojis, Lock screen and widget integration, Journal entries with photos and notes, Weekly, monthly, and yearly reports, CSV export of reports, Home screen widgets

**Features:** macOS Compatibility, Apple Watch app, Vision Pro support

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| KKUK Premium Monthly | $1.99 | per month |
| KKUK Premium Yearly | $12.99 | per year |


### Sumbi

[App page](https://appshunter.io/ios/app/sumbi-study-focus-timer/id6802502926)

This app encourages users to spend less time on their phones by gamifying digital detox. Users engage in timed "dives" away from their devices, earning virtual sea creatures based on their focus duration. It offers a peaceful, non-punitive approach to building healthier digital habits.

**Highlights:** Timed phone-free dives, Unlock virtual sea creatures, Personalized ocean environment, Buddy dive feature, Night sea creatures, Diary-like dive log

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Shallow Sea Creature | $0.99 | one-time |
| Deep Sea Creature | $1.99 | one-time |
| Abyssal Creature | $2.99 | one-time |


## Frequently asked questions

### Is KKUK free?

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

### Is Sumbi free?

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

### Do KKUK or Sumbi have ads?

KKUK shows ads; Sumbi does not.

### Which is updated more often, KKUK or Sumbi?

KKUK ships an update every 5 days, and Sumbi weekly. Most recently, KKUK was updated on October 31, 2026 and Sumbi on October 31, 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.*