User guide

Welcome to It Sinks In!


If you're new to It Sinks In, here's the fastest way to get started:

  1. Create an account.
  2. Click "Add" in the top right.
  3. Fill in the prompt and the answer. (We'll use this example: "What is the capital of Switzerland?")
  4. Optionally, you can add a "Tag" to the question. This lets you group questions by category. You can study categories individually, or you can study all your cards together as they come due.
  5. Optionally, you can add "Variants" to the question. These are different ways of presenting the prompt. Ideally, they present the same essential information in a different way. The goal is to test the same information, while preventing your brain from training itself on an accidental feature of the presentation of the information. So, in our example, you might add "The capital of Switzerland:" and "Switzerland's capital is ___" as variants. Again, this is totally optional.
  6. Click on "Study" in the top right. You should see your prompt there. When you have an answer in mind, click the "View answer" button.
  7. You'll see the answer along with buttons to click if you got the answer right or wrong. Choose the appropriate one.

Spaced repetition

It Sinks In uses a spaced repetition scheduling algorithm.

What is spaced repetition?

Spaced repetition is a technique for optimizing when you review flashcards (or anything else you want to learn). It allows you to learn more information in the same amount of time or to learn the same information in less time.

Where can I learn more about spaced repetition?

  1. From Wikipedia.
  2. From Gwern (includes links to the scientific literature).

What makes It Sinks In different?

Speed and low friction

It Sinks In works quickly: you don't spend time syncing or moving between sets of material. It also supports keyboard shortcuts to help you review material at the speed of thought.


Learners often suffer from learning associations based on the surface structure of a prompt instead of the underlying material. It Sinks In helps with this by allowing you to define variant forms of the prompt. At review time, one form is chosen at random. For example, for the prompt "Who became King of England in 1936?," you could add variants "became King of England in 1936" and "1936: who ascended to the throne of United Kingdom?"


Spaced repetition systems can suffer from accidental clusterings of cards: if you add several cards at the same time, you often end up reviewing them at the same time. This can train your brain into using context that won't always be available. It Sinks In can "jitter" (randomly, but slightly, perturb) the review times in order to break these clusterings. (But you can deactivate this feature if you don't want it.)

Optional advance review

If the optimal amount of time to wait between reviews is 45 days, it's almost as good to wait for 44 days. It Sinks In allows you to review ahead. If you do so, its algorithms will adjust future review intervals accordingly.


The keyboard shortcuts don't work on Chrome.

Are you using an extension (e.g., Vimium) that overrides them?