Flashcards

How spaced repetition works

You forget a new fact quickly, then more slowly each time you successfully recall it. Spaced repetition uses that: instead of reviewing every card every day, it shows each card again just before you would be likely to forget it, and pushes the next review further out each time you remember. A deck of a few hundred cards then costs a few minutes a day rather than an hour.

This tool schedules with FSRS (the Free Spaced Repetition Scheduler), version 5, with its published default parameters. FSRS keeps two numbers per card. Stability is how many days it takes for your chance of recalling the card to fall to 90%. Difficulty, from 1 to 10, is how hard that card is for you. Every answer updates both, and the next review is set for the day your predicted recall drops to 90%.

The four answers

Flip a card, then say how it went. Each button shows how long the card will be away if you pick it.

• Again: you did not remember it. The card comes back before this session ends, and soon after.
• Hard: you got it, with effort. A shorter gap than Good.
• Good: you remembered it. The normal answer.
• Easy: it was effortless. A much longer gap.

For a brand-new card the four answers schedule it 1, 2, 3 and 16 days away. Answer Good on day 3 and the next gap is 11 days. If you then forget it on day 14, Again brings it back after 2 days rather than starting over, because FSRS remembers that you knew it once.

On a keyboard, press Space to show the answer and 1 to 4 to pick Again, Hard, Good or Easy.

New cards and due cards

Each session shows the cards that are due first, the most overdue first, then up to 20 new cards a day per deck, in the order you added them. The limit stops a 500-card import from arriving as one session. A deck shows how many cards are due and how many new ones today's session would add.

Importing and exporting

Import a CSV file with one card per line: front,back, with an optional third column of tags separated by spaces. A first line of front,back is treated as a header. Tab-separated text, which is what Anki's “Notes in Plain Text” export produces, works too. Export CSV writes the same format, so you can edit a deck in a spreadsheet and bring it back. Anki's .apkg package files are not supported.

Sharing a deck

Share as link puts the deck's cards into the page address, after the #, which browsers do not send to any server. Anyone who opens the link sees an offer to add a copy to their own decks. Only the cards travel: your answers and schedule stay with you. A link carries at most 200 cards, to stay short enough to paste into a message.

Where your cards are kept

Decks, cards and every answer you give are stored in this browser's IndexedDB. Nothing is sent anywhere unless you sign in with Google, in which case they are also kept in your own Google Drive's hidden app-data folder and synced between your devices. Your answers are kept as a list, and each card's schedule is worked out from that list, so reviewing on your phone and your laptop while offline merges cleanly once both are back online.