Build a Flashcard App With Spaced Repetition (Claude Writes the Algorithm)

Anki-style studying without Anki: build a flashcard app where Claude implements the spaced-repetition scheduling — and generates your card decks too.

DifficultyBeginner+

Time2 hours

You'll needClaude (free tier works) · A browser · Something you're studying

You'll buildA study app with card decks, flip-to-reveal cards, again/hard/good/easy grading, and a real spaced-repetition scheduler that surfaces cards right before you'd forget them.

Spaced repetition is the most evidence-backed study technique that exists, and the apps built on it are either clunky (Anki) or subscription-walled. The scheduling algorithm behind them is forty lines of code that Claude knows by heart. You're two hours from a study tool tuned to exactly what you're learning — language vocab, anatomy, bar exam rules, Torah verses, anything.

Step 1 — Build the app

Build a flashcard study app as a single HTML file, no external libraries. Features: multiple named decks; cards with front/back; study mode that shows the front, flips on tap/space, then offers Again / Hard / Good / Easy buttons; scheduling via a simplified SM-2 spaced repetition algorithm (interval and ease factor per card — explain your implementation in comments); a due-today counter per deck; add/edit/delete cards; everything in localStorage with JSON export/import. Keyboard shortcuts: space to flip, 1–4 to grade. Clean, focused design — studying should feel calm. Complete file please.

Test the scheduler immediately: grade a card 'Again' and confirm it comes back this session; grade one 'Easy' and confirm its next-due date jumped days ahead. If the behavior feels wrong, describe the symptom — 'Easy cards are coming back tomorrow instead of in 4+ days' — and let Claude fix its own algorithm.

Step 2 — Let Claude write your decks

Here's where this beats every commercial app: your card-generation engine is the same AI that built the app. In a chat:

Generate 40 flashcards for [the Hebrew vocabulary in Genesis chapters 1–3 / California real estate license exam: agency law / muscle origins and insertions of the forearm]. Format as JSON matching this structure from my app: [paste one card object from your export file]. Fronts should be prompts, backs should be concise answers — no paragraph dumps. Make wrong-answer-prone distinctions into their own cards.

Then use your app's Import button. Spot-check facts before trusting a deck — AI-generated cards inherit AI-generated errors, and you'll be memorizing them efficiently.

Worth knowingThe best prompt addition for card quality: 'apply the minimum information principle — one fact per card, and turn lists into multiple cloze-style cards.' That single instruction is most of what separates decks that work from decks that don't.

Step 3 — Make it fit how you study

Iterate: reversed cards (back→front) generated automatically for language decks; a daily new-card limit so day one doesn't bury you; image support on card backs; a stats page showing reviews per day and retention rate; a cram mode that ignores scheduling before an exam. Each is one request.

Step 4 — Study anywhere

Host it (free static hosting works — see the hosting guide), add to your phone's home screen, and your reviews are with you in every queue and waiting room. Since data is per-device localStorage, pick a primary study device, or graduate to the Supabase pattern when you want your laptop and phone sharing one deck state.

Why this one matters

This is the first tutorial where the app and the AI form a loop: Claude built the tool, Claude fills the tool, and the tool makes the knowledge stick. That loop — software shaped around your exact learning, content generated on demand — simply didn't exist for normal people until now.

Keep going

Need somewhere to put it live? See where to host AI-built sites. Compare tool costs on the pricing tracker (or stick to the free options), then pick your next build.