The Leitner Box system is a spaced repetition method developed by Sebastian Leitner in the 1970s. Flashcards are sorted into boxes based on how well you know them. Cards in Box 1 are reviewed daily; if answered correctly, they move up to Box 2 (reviewed every 2 days), then Box 3 (4 days), Box 4 (7 days), and Box 5 (14 days). Incorrect cards always return to Box 1. This ensures you spend more time on difficult material and less on what you already know.

Spaced repetition leverages the psychological spacing effect—information is better retained when reviewed at increasing intervals just before you're about to forget it. By challenging your brain to recall information at optimal moments, you strengthen neural pathways, making long-term retention significantly more efficient than cramming or random review schedules.

Anki uses a more complex algorithm (SM-2) with ease factors and variable intervals. This Leitner Box tool uses the classic 5-box system with fixed intervals (1, 2, 4, 7, 14 days), making it simpler and more predictable. It's ideal for learners who prefer a straightforward, transparent system without complex settings. All data is stored locally in your browser—no account needed.

Check the tool daily—the box overview shows how many cards are due in each box (look for the pulsing red dot). Box 1 cards need daily attention, while Box 5 cards only appear every two weeks. A daily 5-10 minute review habit is far more effective than marathon sessions. The built-in timer helps you track your review sessions.

When you correctly recall a Box 5 card, it stays in Box 5 but its next review is scheduled 30 days out—essentially marking it as mastered. You can still find it in your card list. If you later forget it during a review, it drops back to Box 1 to be relearned. This ensures even "mastered" knowledge gets occasional reinforcement.

Yes! Use the Export button to download all your flashcards as a JSON file. You can later import them using the Import button—great for backups or transferring between devices. All data is also automatically saved to your browser's local storage, so your cards persist between visits on the same device.

During review mode, use Space to flip the card and reveal the answer, Left Arrow (←) to mark as forgotten, Right Arrow (→) to mark as remembered, and Down Arrow (↓) to skip. These shortcuts make desktop review fast and efficient without touching the mouse.