A flashcard app needs no server and no content, people add their own words and questions. There is money in the niche. Quizlet makes $2.47M–9.86M a month by our estimate (not Apple data, October 16, 2026), and AnkiMobile sells for $24.99 as a single purchase and was number 1 among paid Education apps in the US through September and October 2026. The core of the code is the review schedule.
How much study apps make
There is money, and the leader has a lot of it. On October 16, 2026 Quizlet was number 4 in the US top grossing Education chart. Next to it are apps in nearby formats. Vocabulary teaches a word a day, Gizmo and Knowt make cards and quizzes with AI.
| App | Released | US ratings | Price | Top grossing rank | Monthly revenue, our estimate |
|---|---|---|---|---|---|
| Quizlet | Aug 9, 2012 | 1,131,517 | free | #4 | $2.47M–9.86M |
| Vocabulary (daily words) | Feb 19, 2016 | 220,069 | free | #19 | $498K–1.99M |
| Gizmo (AI tutor) | Feb 17, 2022 | 13,849 | free | #23 | rating spike, no estimate |
| Knowt (AI flashcards) | Oct 13, 2023 | 11,027 | free | outside top 100 | $91K–366K |
| AnkiMobile | May 27, 2010 | 2,359 | $24.99 | #45 | paid, $24.99, no estimate |
Appto data as of October 16, 2026. Rating growth September 16 to October 16, 2026. Rating counts and chart positions from the US App Store on October 16, 2026. Revenue is our estimate, not Apple data.
Knowt launched on October 13, 2023 and gathered 11,027 ratings in three years. By our estimate it makes $91K–366K a month. Gizmo was number 23 in the category's top grossing chart on October 16, 2026, and we have no estimate for it because its ratings spiked in the window.
AnkiMobile sells without a subscription
The most telling app in the niche is AnkiMobile. It costs $24.99 to download, has no subscription, and its last update came out on September 8, 2025. Even so, in all four weekly snapshots from September 24 to October 15, 2026 it was number 1 among paid Education apps in the US and between number 8 and 11 among paid apps in all categories.
It has few ratings, 2,359 ratings in the US. People pay for a proven method, the looks matter less. That is a good sign for a newcomer. A one-time purchase works in this niche when the app does its main job reliably.
How spaced repetition works
Most of these apps are built on SM-2, the algorithm Piotr Woźniak described for SuperMemo in 1987 (description on the SuperMemo site). The first review comes after one day, the second after six days, and after that the interval is multiplied by the card's easiness factor. A new card starts at 2.5, and the factor drops to 1.3 if the person keeps getting it wrong. After each answer the person grades it, and the grade moves the factor.
There is also a newer open algorithm, FSRS. Anki has had it built in since version 23.10 (Anki manual). SM-2 is enough for version 1, its calculation takes a few dozen lines of code. For every card, store the next review date, the interval and the factor.
What goes into version 1
- Decks and a card editor. Question and answer as text, an image if needed. People bring the content, so you prepare no material for the app.
- Today's queue. The main screen says how many cards are due now. Grade the answer with three or four buttons.
- Scheduling on the device. SM-2 computes the dates locally, everything works offline.
- Import from a spreadsheet. Bringing a deck in from CSV removes the main fear of switching apps.
- A daily reminder. A local notification, no server needed.
Sync between devices can wait. When you need it, CloudKit keeps the data in the person's own iCloud, so you don't have to run a server.
How the niche charges
Both models work here. Quizlet and Knowt are free to download and charge inside the app. AnkiMobile costs $24.99 once and Flashcards Deluxe $4.99 (US App Store, October 16, 2026). If the app spends nothing on servers or AI, the fair model is a few decks for free and everything else for a single purchase.
Risks
- The general query is taken. Quizlet has 1,131,517 ratings in the US. People find a newcomer through narrow queries, such as a subject or an exam.
- AI flashcards. Knowt and Gizmo sell cards generated from notes. Out-smarting them is hard, it is easier to stand out with privacy and offline use.
- Anki users expect import. The .apkg format is an archive with an SQLite database. If you have no import, say so on the App Store page up front.
How we counted
Appto estimates revenue from 30 days of App Store rating growth, before Apple's commission. It is our estimate, not Apple data. In half of the cases the estimate is within 2x of the real figure, in four out of five within 3x, and for large apps it tends to run low. Ads, web sales and Google Play are not included. The method is explained in our article on estimating app revenue.
Next steps
This niche is number 12 in the book 50 iPhone App Niches. The book has an angle for a newcomer, a five-screen plan for version 1 and a task you can hand to the agent.
You can run the app itself in Appto. Appto rechecks the niche on fresh App Store data, builds the screens and the code with the agent, writes the store page in the languages you need and submits the build to Apple from your account or shows you what to press in App Store Connect.
Questions
How much do flashcard apps make?
By our estimate Quizlet makes $2.47M–9.86M a month and Knowt $91K–366K (October 16, 2026). It is an estimate from App Store rating growth, not Apple data.
Which repetition algorithm should I use?
Start with SM-2. It is open, described on the SuperMemo site and takes a few dozen lines of code. FSRS is more accurate and can come in version 2.
Do I need a server?
No. Cards and the schedule live on the phone and the reminder is local. Sync can go through CloudKit in the person's own iCloud.
Can I sell without a subscription?
Yes. AnkiMobile costs $24.99 as one purchase and from September 24 to October 15, 2026 it was number 1 among paid Education apps in the US.
How do I stand out from Quizlet?
With a narrow topic and what the leader lacks. Offline use, a single purchase, import of your own spreadsheets and privacy without an account.
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