Comparison

KKUK vs Sumbi

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

KKUK

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
Read full description

A to-do list erases what you finish. KKUK does the opposite — every day you follow through leaves one more stamp. Press one stamp today. Then watch them stack up on the calendar. ■ Press it without opening the app Open the app once and today's board appears on the Lock Screen and in the Dynamic Island. For a while after that you can press a stamp right there, without going back to the app. You can also press one from a Home Screen widget. ■ A press, not a tap One quick tap won't do it. Hold your finger until the ink fills all the way, and the stamp lands. Slide your finger aside to cancel a press you didn't mean. ■ Make your own stamp Build a stamp from 16 colors and an emoji. Which weekdays, how many times a day, which group it belongs to, and when it should remind you — set all of it per stamp. ■ See what you've kept · Calendar — every stamp you pressed this month on a single board. · Journal — leave a note and a photo beside the stamp. · Report — see how well you kept up by week, by month, and by year. The period you're looking at can be exported as a CSV file. · Monthly review — look back on the month that just ended. ■ Seven Home Screen widgets Today's Stamps · Recent check-ins · Calendar · Weekly report · Monthly report · Group weekly · Large calendar. Pick any size and keep it on your Home Screen. ■ Make it yours Twenty bundled typefaces — four drawn for Latin text, sixteen Korean. Light, dark, or follow your device. Portrait only. ■ Free to use 3 stamps, 3 groups, the last 30 days of records, this week's and this month's report, and the Today's Stamps widget. Watch a rewarded ad all the way through to add one more stamp, and the slot you earned stays yours. ■ KKUK Premium unlocks · Unlimited stamps and groups · Every record, including anything older than 30 days · Past reports and past monthly reviews · All seven widgets · iCloud sync to continue on another device · No ads ■ Subscription details · KKUK Premium Monthly — $1.99 / month · KKUK Premium Yearly — $12.99 / year Subscriptions renew automatically. Unless canceled at least 24 hours before the current period ends, a subscription renews at the same price, and payment is charged to your Apple Account at confirmation of purchase. You can manage or cancel subscriptions in Settings > Apple Account > Subscriptions on your device. Terms of Use https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy https://kkuk-app.web.app/en/privacy/ ■ Your records stay on your device Stamps, notes, and photos are stored on your device. There is no account and no sign-in. iCloud sync is off by default, and when you turn it on, records are copied only to your own private iCloud database. The developer cannot read them and does not keep them on a separate server.

About

Sumbi

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
Read full description

The longer you put your phone down, the deeper your life gets. Start the timer, set your phone down, and sea creatures come to your ocean. From exam prep to digital detox, dive with Sumbi. Sumbi is a study focus timer and digital detox app named after the "sumbisori," the whistling breath of Jeju haenyeo, Korea's legendary free-diving women. Start a dive when you want time away from your phone. While your phone rests, your ocean deepens, and sea creatures come to live in it. Who dives with Sumbi - Students who need a study timer for exams and deep focus - Anyone fighting phone addiction or doomscrolling - People who want to cut screen time and rebuild concentration - ADHD brains that need a gentle, visual reason to stay off the phone - Anyone who just wants to watch a calm ocean and breathe What makes Sumbi different 1. One dive = one focus session. Keep your phone down while the timer runs, and the dive succeeds. If you fail, nobody scolds you. 2. Your focus time becomes an ocean. Successful dives bring creatures from shallow water, deep water, even the abyss. 3. Collect and raise your sea creatures. The more you dive, the wider and deeper your ocean grows. 4. Gift creatures to your dive buddies. Focus is deeper together. 5. No ads, no noise. Sumbi never drags you back with notifications. Coming back is your choice. Study timer, pomodoro, or deep work Pick any length with the dial: a short pomodoro-style session or hours of exam prep. Every dive adds to your daily focus record. When haenyeo divers surface, they release a long whistling breath: "hooo-ee." Your day deserves a breath that deep. Have a good dive. Hoo-ee! Contact: sumbi@niceday.io

Screenshots

KKUK4 screens
Sumbi4 screens

Verdict

The call

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.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

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.

UpkeepUpdate frequency

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

Scorecard3 real differences · 7 level
KKUK versus Sumbi: the parameters behind the verdict, then further details
ParameterKKUKSumbi
PriceFreeFree
Rating—5.0 (1 ratings) — better
Positive reviews100.0% of reviews100.0% of reviews
Number of ratings—1 — better
Update frequencyEvery 5 days — betterWeekly
AdsYesNo — better
In-app purchasesYesYes
MonetizationFree with in-app purchasesFree — better
DevicesiPhone, Apple Watch — betteriPhone
Requires iOS18.016.4 — better
Further details — not scored
Size82 MB94 MB
Age rating4+4+
DeveloperSangcheol Kim나이스데이

Customer experience

KKUK

Written reviews1 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

Sumbi

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews18 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

2 purchases

KKUK

Subscriptions2
  • KKUK Premium Monthly$1.991 Month
  • KKUK Premium Yearly$12.991 Year
3 purchases

Sumbi

One-time3
  • Shallow Sea Creature$0.99
  • Deep Sea Creature$1.99
  • Abyssal Creature$2.99

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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