Spaced Repetition Algorithms: How Anki Actually Works

Spaced repetition gets marketed like a cheat code. Install Anki. Add cards. Press buttons. Knowledge sticks forever. Students who struggle with memory grab onto this idea because it promises control.

Then reality hits.

Cards pile up. Reviews feel endless. Some facts stick, others don’t. Motivation drops. Students start blaming themselves or the app.

The problem is not Anki. The problem is misunderstanding what it actually does.

Human memory fades in patterns. Information is easiest to forget shortly after learning and stabilizes when recalled at the right moments.

Spaced repetition exploits this by reviewing information just before it is likely to be forgotten.

Not too early. Not too late.

That timing is the entire system.

Anki does not work because of spacing alone. It works because it forces active recall. You must retrieve information from memory before seeing the answer.

Reading feels productive. Recall feels uncomfortable. Learning happens in the uncomfortable part.

Anki does not measure how important a fact is. It measures how well you remember it.

Every time you review a card, you tell Anki how it felt:

These buttons are not cosmetic. They feed an algorithm that estimates how strong that memory is in your brain.

Anki schedules the next review based on that estimate.

When you recall a card successfully, Anki increases the interval before you see it again. Fail, and the interval shrinks.

Over time, strong memories move weeks or months apart. Weak ones return quickly.

This is why review loads feel heavy at first and lighter later if used correctly.

Students often dump entire textbooks into Anki. Long definitions. Paragraphs. Complex explanations.

Anki is not designed for reading. It is designed for testing.

If a card cannot be answered clearly in a few seconds, it is probably badly designed.

Cards that allow recognition defeat the system. If the answer feels obvious when you see it, the card is not testing memory.

Good cards make you think before revealing the answer. Bad cards let you nod and move on.

Recognition builds confidence. Recall builds memory.

If students press “Easy” to finish faster, the algorithm assumes the memory is strong. It schedules the next review far away.

The result is predictable. The card comes back weeks later and is forgotten.

Anki punishes dishonesty quietly and effectively.

The algorithm assumes regular use. Skipping days stacks reviews and overwhelms students.

Anki works best when treated like brushing teeth. Short, daily, non-negotiable.

Cramming with spaced repetition breaks the system.

Anki excels at things that have clear answers. Vocabulary, biological pathways, laws, dates, formulas.

If something can be tested cleanly, Anki handles it well.

Spaced repetition is ideal for topics that keep slipping away. It targets forgetting efficiently instead of reviewing everything equally.

Anki does not teach reasoning. It does not build intuition. It cannot replace practice or explanation.

Using Anki alone for conceptual subjects leads to shallow learning.

Spaced repetition supports understanding. It does not create it.

The algorithm cannot fix bad inputs. Vague questions produce vague learning.

Anki amplifies quality. It does not create it.

Students should create fewer, sharper cards. One idea per card. Clear question. Clear answer.

If a card feels annoying to review, it probably needs rewriting.

Learn from books, classes, or videos first. Understand the topic. Then encode key points into Anki.

Using Anki to learn from zero is inefficient and frustrating.

Anki is not a learning system. It is a memory maintenance system.

It keeps what you already understand from disappearing.

When students respect that role, spaced repetition becomes powerful and sustainable. When they expect it to replace thinking, it becomes exhausting.

The algorithm is not intelligent. It is obedient.

It does exactly what your behavior teaches it to do.