OneLine. one line a day, in Korean

Write one line a day.

A prompt lands on your lock screen. You answer it in one sentence — then hear how a native would have said it.

Now live on iPhone Download on the App Store Also on Android Get it on Google Play

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One sentence a day is the floor, not the ceiling.

Write more on the days you feel like it. Never because we asked you to. One line keeps the run alive, and that is the entire design — the smallest ask we could make that still teaches you something.

One line, followed through

One prompt, one sentence, and everything it leaves behind — in the order you'd actually meet it.

  1. 8:40, day one

    It arrives on your lock screen

    A new question each day, written for your level. Nothing to open, no session to start — it's just there when you pick up your phone.

    8:40
    OneLine now

    Today's prompt

    주말에 누가 놀러 왔어요?

  2. 8:41

    You answer it in whatever time you've got

    Most days the notification is the whole thing: one sentence, sent, phone never unlocked. That's the floor, and it's enough to keep the run going.

    On a day when you've got five minutes, open the app instead: the same prompt with room to think, and on Pro, examples, patterns and the words for this exact prompt one tap under your line.

    Busy day · 30 seconds
    8:41
    OneLine now

    주말에 누가 놀러 왔어요?

    제 친구는 놀러 왔어요.
    A day with time · five minutes
    Today's prompt

    주말에 누가 놀러 왔어요?

    주말에 친구가 놀러 왔어요. 같이 영화를
    22/500
    Examples Patterns Words Pro

    사촌이 놀러 와서 같이 저녁을 먹었어요.

    My cousin came over, so we had dinner together.

    Models to adapt — yours can be totally different.

  3. About five seconds later

    You hear it said right

    Either way, the coach comes back the same: it leads with what worked, then shows the one thing a native would have done differently — at whatever strictness you asked for.

    Then it reads your line back to you. Press play; that's the real voice.

    Nice — one small fix:
    Natural version

    제 친구가 놀러 왔어요.

  4. A week in

    Keep a word. The blank asks for it back.

    Any word you meet while writing goes on your shelf with one tap — no decks to build, no schedule to fall behind on.

    Later, a sentence turns up with that word missing and you put it back. That's the whole exercise. You can stop after one.

    My words Practice
    주말 weekend
    놀다 to hang out

    이번 주말에 뭐 해요?

    What are you doing this weekend?

    Yes — that's it. 주말 — weekend
  5. Whenever you're curious

    The grammar underneath, all of it

    Every Korean pattern from A1 to B2, in one plain list you can read straight through — what it does, and a sentence that uses it.

    Bookmark the ones you're working on and they sit at the top, next to your words.

    SavedAll
    N이/가 — subject marker

    Marks the grammatical subject — new information, or the thing that is or does.

    A1
    -아/어요 — polite present

    Everyday polite present, for actions and descriptions alike.

    A1
    -았/었어요 — past tense

    Completed actions and past states.

    A2
  6. A month in

    And the mistake you keep making

    OneLine watches what comes back more than once across ninety days of corrections, and shows you your own sentence where it slipped.

    No grade, no percentage, no streak to protect. Just the short list of what to watch for.

    은/는 vs. 이/가

    Keeps coming up · 4 times · last Tuesday

    You wrote 저는 커피가 좋아요

    -았/었어요 — past tense

    2 times · yesterday

    You wrote 어제 학교에 가요
  7. The whole time

    And the days, counted honestly

    A month at a glance: every day you wrote, your current run, your best one. The numbers are real — we'd rather show you a small true one than a big invented one.

    Miss a day and you can still go back and answer it. Do that within three days and the run keeps going.

What it costs

Free, forever

  • Today's prompt, and hearing it read aloud
  • Writing your line and saving it
  • Your streak, your calendar, and catching up a missed day
  • Every line you've written, kept with its correction
  • Keeping words, and fill-the-blank practice
  • The whole A1–B2 pattern guide
  • Where you slip — the mistakes that keep coming back

Pro adds

  • Coaching on every line you write, at any strictness
  • Your corrected line read aloud
  • Words to try before you write
  • Writing about a topic you choose
  • Write-your-own practice with your kept words

Seven coached corrections are free to start with, and they don't expire. After that, writing, saving and your streak carry on exactly as before. No ads, and nothing you have to buy to keep the habit.

FAQ

Is OneLine free?

The daily prompt, hearing it read aloud, writing, saving, and your streak are free and always will be. Seven coached corrections are free to start with, and they don't expire — after that, coaching is the part that's Pro.

Which language?

Korean at launch, from complete beginner up to advanced. Spanish, French and German are next.

Do I need an account?

Not to start. You write your first line without signing up for anything. Make an account whenever you like and every line and every day you've already written comes with you.

How much time does it take?

Setup is under 45 seconds. After that most days are under a minute, and a lot of it happens right in the notification without opening the app.

What if I miss a day?

You can still go back and answer it — the line fills in on the day it belonged to, so your archive stays true. Do it within three days and your run keeps going.

Which phones?

iPhone and Android, together at launch.