Comparison

iStackz vs Sabai

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

Head to head
About

iStackz

Features
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Flashcard organizer, classifying cards in 5 levels from unknown to known. The color of the cards represents a characteristic of the card, typically the duration since the last positive test: the card turns darker over time, indicating the need to refresh it from time to time. This is very useful when e.g. learning Japanese kanji where a large set of characters must be kept in memory. Other color modes provide more detailed means to highlight cards prominently that must be refreshed, or represent the numbers of successes or failures. The app provides tools for testing and learning. Testing is used to assess the proficiency state of the cards, by moving it to the right side (known) or left side (unknown) with the arrow buttons, or by directly dragging the card on the screen. Learning is used to iterate through a short, growing list of cards until the new words are mastered sufficiently for the moment. The next testing session will show if the words stick. Every card has up to four attributes, which can be aligned in specific sequences in the testing and learning tools, to individually train specific skills. In addition to the displayed text, the attributes can be presented in a read aloud form with the text-to-speech function of iOS, with fully customized voices in all supported languages. A growing archive of wordlists is available on the homepage (stackz.com), or new wordlists can be created with the free Stackz List Editor on Windows. Card decks can be downloaded to the Apple Watch, where the card texts can be displayed continuously in the watch face complications for ongoing repetition - tapping on the text in the watch face opens the Stackz watch app to display all attributes of the card.

About

Sabai

Learn Thai effortlessly with daily words appearing on your phone's lock screen. This app integrates language learning into your daily routine without pressure, offering pronunciation, meaning, and practice tools.

Highlights
  • Lock screen widget for daily words
  • Thai script, pronunciation, and meaning
  • Customizable word frequency
  • Flashcard practice
  • Learning progress tracking
  • Favorite words and streaks
Read full description

Learn Thai the easy way: a few new words a day, right on your Lock Screen. You pick them up just by glancing at your phone. No lessons, no pressure, no daily grind. Sabai makes Thai part of your everyday life. Useful Thai words show up on your phone throughout the day, so the language feels a little more familiar every time you check your screen. HOW IT WORKS • Add the Sabai widget to your Lock Screen or Home Screen • Each word comes with Thai script, easy pronunciation and its meaning • Choose how many new words you want a day and when your Lock Screen words change • Tap a word in the app to hear it spoken by a natural Thai voice LEARN AT YOUR OWN PACE • Practice with simple flashcards • Mark words as Learned, Almost Got It or Still Learning, and Sabai brings back the ones you need • Save your favourites, keep your streak and watch your progress grow No account needed. Your learning progress stays on your device. Terms: https://sabailearn.com/terms Privacy Policy: https://sabailearn.com/privacy

Screenshots

iStackz4 screens
Sabai4 screens

Verdict

The call

The clearest difference is update cadence: Sabai at weekly against iStackz's every 4 weeks. On price, ads, in-app purchases and device support 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. iStackz sells 1 in-app purchase, starting at $1.99 per month and Sabai sells 2 in-app purchases, starting at $4.99 per month. Whichever you choose, the download price is not the number that matters.

UpkeepUpdate frequency

iStackz ships an update every 4 weeks, Sabai weekly. The most recent releases landed on October 29, 2026 and October 31, 2026 respectively.

Scorecard1 real difference · 8 level
iStackz versus Sabai: the parameters behind the verdict, then further details
ParameteriStackzSabai
PriceFreeFree
Rating—5.0 (1 ratings) — better
Number of ratings—1 — better
Update frequencyEvery 4 weeksWeekly — better
AdsNoNo
In-app purchasesYesYes
Monetization—Freemium
DevicesiPhone, Apple Watch — betteriPhone
Requires iOS17.617.0 — better
Further details — not scored
Size3 MB48 MB
Age rating4+4+
DeveloperChristoph LuediLuis Halama

In-app purchases

1 purchases

iStackz

Subscriptions1
  • Full functionality - monthly$1.991 Month
2 purchases

Sabai

Subscriptions2
  • Sabai Premium (Monthly)$4.991 Month
  • Sabai Premium (Yearly)7 Days trial$17.991 Year

Questions

Is iStackz free?
iStackz is free to download, with in-app purchases available.
Is Sabai free?
Sabai is free to download, with in-app purchases available.
Do iStackz or Sabai have ads?
Neither iStackz nor Sabai shows ads.
Which is updated more often, iStackz or Sabai?
iStackz ships an update every 4 weeks, and Sabai weekly. Most recently, iStackz was updated on October 29, 2026 and Sabai on October 31, 2026.

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