Spaced repetition is an evidence-based learning technique [Pedagogy] that is usually performed with flashcards. Newly introduced and more difficult flashcards are shown more frequently, while older and less difficult flashcards are shown less frequently in order to exploit the psychological spacing effect [Spacing effect]. The use of spaced repetition has been proven to increase rate of learning.


The basis for spaced repetition research was laid by Hermann Ebbinghaus, who suggested that information loss over time follows a forgetting curve [Forgetting curve], but that forgetting could be reset with repetition based on active recall.

(“Spaced Repetition” 2022)

Also see Testing effect and Purposeful practice. This is one of my Favorites.

Spaced repetition is how I bring intention to memory: I remember the things I choose to remember, rather than only the things I happen to remember. It aids in making learning and memory conscious, effortful, process.

Note The difference between knowing the name of something and knowing something. Spaced repetition is capable of aiding both remembering names and deeper understanding. However, the two require different approaches:

  • Remember something when prompted (e.g. knowing the definition of a word while reading)
  • Bring an idea to mind in context (e.g. using a word while writing)

It’s most effective when the practice mirrors, as closely as is possible, the way the knowledge will be applied (see also Desirable difficulty).


My preferred solution is org-fc. However, Anki is, as far as I can tell, the most popular and well known. I used Anki exclusively prior to switching to org-fc.

As far as I can tell, from my own experience and reading what others have written on the topic:

  1. It’s not popular because it isn’t popular

    People are not strategic by default and aren’t likely to go out on their own to pursue novel (to them at least) ways of doing something. They’re much more likely to do what they see others doing.

  2. Other, more popular, learning methods work well enough

    Spaced repetition isn’t the only effective way to learn a topic. Additionally, those alternatives often feel better in the moment or give the impression that they’re more effective:

    Of course, [cramming] is precisely what students do. They cram the night before the test, and a month later can’t remember anything. So why do people do it? (I’m not innocent myself.) Why is spaced repetition so dreadfully unpopular, even among the people who try it once?⁠

    Because it does work. Sort of. Cramming is a trade-off: you trade a strong memory now for weak memory later. (Very weak⁠⁠.) And tests are usually of all the new material, with occasional old questions, so this strategy pays off! […]

    (Branwen 2009)

  3. It’s hard to write good, effective, cards

    One reason this can be frustrating is you’ll often remember a flashcard for the first few weeks of it (when you’re seeing it with high frequency), but after a couple of months, you start failing it. It didn’t take root in your long term memory, because it was poorly written in some way. And this long feedback cycle means it takes time to acquire these skills through trial and error.

    (Borretti 2023)

  4. Spaced repetition is a form of delayed gratification

  5. “For spaced repetition to be useful, it has to be a habit” (Borretti 2023) and it’s a difficult habit to form

On writing cards

Extend based on (Borretti 2023)

Cards should be small

Cards, like Evergreen notes, should be atomic; they should test a single, small, idea.

Approach an idea from more than one direction

On sequences

Refer to (Borretti 2023)

Also see org-fc’s context card

On hierarchies

Refer to (Borretti 2023)


Borretti, Fernando. 2023. “Effective Spaced Repetition.” Fernando Borretti.
Branwen, Gwern. 2009. “Spaced Repetition for Efficient Learning,” March.
“Spaced Repetition.” 2022. Wikipedia, January.