Ever shelved a vocabulary book with the first thirty pages black with notes and the rest still spotless?
The problem isn't willpower. It's order. Nobody can tell by feel what to review and when. HaruHaru is a Korean vocabulary website that does that math for you. It holds 14,096 Korean words, from the Hangul letters through TOPIK (Test of Proficiency in Korean) levels 1–6 and beyond, and all you have to do is today's cards.
“What should I study today?”
The order is already laid out. After the 199 Hangul characters, in the order of vowels, consonants, the syllable chart, and final consonants, come TOPIK 1 through 6 and the words beyond the levels: 14,096 words in days of 50 cards. Just open a day and flip through the cards. The home page remembers how far you got and shows you where to pick up.
The levels are based on the vocabulary grades in the “International Standard Curriculum for Korean Language” by the National Institute of Korean Language, taking into account how often each word is actually used today.
“I saw it once. Why didn't it stick?”
That's simply how memory works.
In 1885, Hermann Ebbinghaus tested himself to measure how fast memories fade, and drew the forgetting curve. Close to half of something new is gone within an hour, and two thirds or more within a day. A word you clearly learned yesterday slipping away today has nothing to do with willpower.
But the curve has a loophole. Recall something just before you forget it, and the curve flattens. Seeing a word once a day for ten days sticks far longer than seeing it ten times in one day. This is called the spacing effect, confirmed by a 2006 meta-analysis of 317 experiments from 184 papers. The same research found that the longer you want to remember something, the wider the gaps should be.
So the real question is when “just before you forget” is. That's not something anyone can guess by feel.
“So when should I see it again?”
The moment your chance of remembering drops to 90%.
HaruHaru draws a separate forgetting curve for every card. The point where the memory has started to blur but isn't gone yet is when you meet the word next. Meet a word after you've fully forgotten it and you're learning it from scratch. Meet it too early and it's still so fresh that nothing gets warmed up. Memories that take effort to recall last longer, so it aims for the point where a single review is worth the most.
Trying to recall the meaning before you see it strengthens memory on its own, far more than reading it again. Those few seconds you pause before flipping a card matter most.
Each time you get a word right, the curve flattens and the next meeting moves further out. A word you just learned comes back in 10 minutes, one you've gotten right a few times in a few days, and one you truly know in a few months. Miss it and the gap shrinks again. Under each grade button you can see when the card will come back, so you know what your answer changes before you press it.
The math is done by FSRS, the spaced repetition algorithm built into Anki. It's a model refined on 700 million reviews from 10,000 real learners, and HaruHaru uses its latest version as is.
“How much do I know right now?”
Every word has a temperature: where it sits on its forgetting curve right now, turned into a color.
A word you just learned is a warm green. One you haven't seen in a while cools through yellow to orange, and one you've missed three or more times sinks to red. Reviewing is warming cold words back up.
We could have used numbers, but didn't. “73%” has to be read and then interpreted; a color takes only a glance. Scroll through a word list and the gaps show themselves. The Hangul chart is colored the same way, so the characters you haven't touched yet stand out right away.
“What if I've never seen Hangul before?”
The 199 Hangul characters come first, in a deck of their own. You learn the basic vowels and basic consonants, read the two together in the syllable chart, and then move on to compound vowels, tense consonants, and final consonants. The Hangul chart is divided into these six groups, so the chart shows you right away which part you're learning.
Every character comes with a native voice and its romanization. The romanization follows the South Korean government's Revised Romanization of Korean, but it's only a guide, so listen to the voice for the actual sound. Consonants are read with ㅏ added, so ㄱ is read as 가. Final consonants make only seven sounds, so the ones that sound the same are grouped in the same column. You can also hide the romanization on the Hangul chart and click the characters one by one to check your guesses.
“What's different about Korean words?”
Many words aren't pronounced the way they're spelled, so when the pronunciation differs, it's written out in Hangul, as in 학교 [학꾜]. You can choose from four voices, two female and two male.
Words that conjugate show their forms together, like 들어요 · 들었어요 · 듣는, and irregular ones are marked. Type 들었어요 or 학교에서 into the search box and you'll still find 듣다 and 학교. Sentence patterns are listed too, with the particles a word usually takes, like ~을/를 듣다.
Loanwords show the word they came from on the back of the card. Different words with the same spelling get a short phrase on the front, like 말을 하다 or 말 한 마리, so you know which word it is the moment you see the card.
“What can I do on the website?”
Open the entire vocabulary right in your browser. Search all 14,096 words by word, conjugated form, or meaning, and follow the levels and days down to one page per word. In the lists you can hide pronunciation and meanings and shuffle them to test yourself, and grading cards gives words a temperature.
There's no sign-up and no login. The temperatures you set stay in that browser only. We're working on a HaruHaru app that makes it easy to keep going every day.
And more
- Audio plays automatically when you flip a card
- Shuffle a list so you don't rely on the order you learned it in
- Light and dark themes
Whether you're a complete beginner starting with Hangul or a test taker organizing words level by level for the TOPIK, you can start with the same vocabulary.
Smart is the site's job. Steady is yours.
Just finish today's cards.