Making a deck
Under Cards, type a question or word on the front and its answer on the back; a new empty row appears as you fill the last one. If your cards are already in a list, switch to Paste a list and put one card per line, with the front and back split by a dash with spaces round it (France - Paris), a tab, or a comma. Each line is split at its first tab, or failing that its first spaced dash, or failing that its first comma, so a back with commas in it is safe after a dash or a tab.
Studying
Switch to Study and the deck is dealt one card at a time. Click the card or press Space to flip it, and use the arrow keys or the arrow buttons to move. When you know a card, press Got it; when you do not, press Again. Either one moves you on, and the bar along the top fills in as the two piles grow. At the end you can study only the Again cards, which is how you drill the ones that have not stuck yet. Shuffle deals the deck in a new order.
The deck is in the link
This page stores nothing on your device. Instead, every change you make is written into the end of the address, after the #. Bookmark the page or press Copy link and the deck comes back when you open it, on any device. Send the link to a classmate and they get the same cards. The part after the # is never sent to a web server, so not even this site sees your cards.
Taking it elsewhere
Download .txt saves the deck as a plain text file with one card per line, the front and back split by a tab. Anki and Quizlet both import that format, and you can paste it straight back in here.
Questions
Is there a limit on the number of cards?
Not a fixed one. Each card makes the link a little longer, and a deck of a few hundred short cards still makes a link that browsers and chat apps handle. For a very large deck, keep the .txt file as well.
Can I add pictures or formatting?
No, the cards are plain text. That keeps the link short enough to share.
Does it remember which cards I got right?
Only while the page is open. The Got it and Again piles are not put in the link, so a shared deck starts fresh for whoever opens it.
Why does the card not turn over for me?
If your device is set to reduce motion, the card swaps sides at once instead of spinning. Everything else works the same.