Brainscape is a spaced-repetition flashcard system (SRS) that allows users to make and share their own cards and decks with the world. Recently, the website has begun to break down decks by subject and users are able to quickly find Japanese-related content very quickly. For example, you can easily find decks about Japanese grammar, Japanese vocabulary, or even for kanji.
The way Brainscape uses SRS is a little different from other, more popular platforms like Anki and Wanikani. While Anki and Wanikani utilize a long-term SRS approach that can span days, weeks, and years, Brainscape's spaced-repetition system uses a short-term approach. Cards are marked with a number from 1 to 5 (1 being "unlearned" and 5 being "learned"). Cards marked with lower numbers will appear more often in the learning queue than those marked with higher numbers. After getting lower-numbered cards correct a few times, you are able to raise the number and get them all to fives. At that point, you can say that you've completed the deck. There is no need to come back to decks later as cards do not naturally fall in number. Since this type of spaced-repetition system is great for getting info into your short-term memory efficiently rather than cementing things into your long-term memory, Brainscape is best to use to get some info into your head quickly. If you need to cram for a test the night before, Brainscape has got your back!