Studying

Recall uses spaced repetition to help you remember more information in significantly less time.

Ratings

When you reveal the back side of a card, you're asked to rate how well you remembered the information. The rating you give determines when you'll see the card again.

• Forgot: You couldn't remember the information, or part of the information.
• Hard: You remembered the information, but found it difficult.
• Good: You remembered the information. This is the default positive rating.
• Easy: You remembered the information easily.

The algorithm

Learning phase

When a card is new, it uses fixed short-term intervals before entering the review phase. Once you've pressed "Good" twice or "Easy" once, the card moves to the review phase.

Review phase

Recall uses the open-source Free Spaced Repetition Scheduler (FSRS) version 4.5 to schedule cards in the review phase.

The goal of FSRS is to predict when the retentiton of a card reaches a target level, so that you review it at the right time. It has been shown to significantly outperforms other spaced repetition algorithms (source).

Study settings

There are a few controls to help you manage the pace of your studying.

Daily new cards

This is the maximum number of new cards added to the reviews each day. However, less cards are added if you already have many cards to review, such as:

Total number of due reviews < Daily new cards * 2.5

Target retention

This is the minimum percentage of cards of your deck that you want to remember at any given time.

The target retention can be set between 70% and 99%. Keep in mind that each additional percentage point over 95% significantly increases the number of reviews.

When you update the target retention, the change is taken into account in the following reviews to calculate the next intervals. It doesn't reschedule all your cards retroactively.

Scheduling or unscheduling cards

You can manually schedule or unschedule cards.

• On the main page of a deck, click on the row of a card.
• During a review, click in the top right corner of the page.

When a card is unscheduled, it's elligible to be automatically added to reviews again after 7 days.