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The FSRS Algorithm

Experience how the Free Spaced Repetition Scheduler optimizes your memory in real-time.

Stop guessing. Start knowing.

Legacy SM-2 algorithms used by older apps are rigid. They treat every card and every brain exactly the same.

FSRS changes everything. It's an optimizer that calculates the exact mathematical probability of you remembering a card, tailoring the schedule to your unique learning curve.

  • Reach 90% retention with 20% fewer reviews.
  • Optimize for your specific test date.
  • Adapt instantly to hard material vs easy material.
Retention Probability over Time

See it in action

Step through a real-world flashcard learning scenario to see how FSRS adapts vs standard algorithms.

Step 1 of 4
Day 1 Next: 10 min

What is the half-life of Carbon-14?

Learning a New Concept

You encounter a new flashcard. FSRS analyzes the content's initial difficulty. You review it and press 'Good'.

FSRS Engine Output
Target Retention:90%
Current Stability:100%
Calculated Interval:10 min