〜ておく comes from the verb 置く（おく, oku）, "to place, to set down," and that image is the key to the whole pattern: you "set an action down" ahead of time so that its result is standing there, ready, when you need it later. English says "do X in advance" or "go ahead and X for later." It's one of the most practical patterns in the language — the grammar of foresight — and it belongs to the て-form auxiliary family.
The core sense: preparation for later
The main use is doing something now for the sake of a future need. The action is deliberate and forward-looking: you book, buy, chill, memorize, or check something so that things are ready down the line.
旅行の前に、ホテルを予約しておいた。
ryokō no mae ni, hoteru o yoyaku shite oita
I booked the hotel in advance, before the trip.
お客さんが来る前に、ビールを冷やしておこう。
okyaku-san ga kuru mae ni, bīru o hiyashite okō
Let's chill the beer before the guests arrive.
テストに出るから、この単語を覚えておいてください。
tesuto ni deru kara, kono tango o oboete oite kudasai
It'll be on the test, so please memorize these words in advance.
The second sense: leaving a state as it is, on purpose
The same "set it down and leave it" logic gives a second, closely related use: deliberately maintaining a state rather than changing it. You leave the window open, leave the light on, leave the dishes where they are — because that's the useful thing to do.
暑いから、窓を開けておこう。
atsui kara, mado o akete okō
It's hot, so let's leave the window open.
お皿はそのままにしておいて。あとで洗うから。
osara wa sono mama ni shite oite. ato de arau kara
Leave the dishes as they are. I'll wash them later.
まだ使うから、パソコンはつけておいてね。
mada tsukau kara, pasokon wa tsukete oite ne
I'm still using it, so leave the computer on, okay?
The difference from the first sense is subtle: sense one creates a readiness (book, chill), sense two preserves a useful state (leave open, leave on). Both are 置く's "let it stand for later."
The casual contraction: 〜とく／〜どく
In speech, 〜ておく almost always contracts. This is not slang you can skip — it's how the pattern actually sounds in conversation, and you'll mishear people if you don't know it.
- 〜ておく → 〜とく (しておく → しとく, 開けておく → 開けとく)
- 〜でおく → 〜どく (読んでおく → 読んどく, 飲んでおく → 飲んどく)
The voicing carries over: a て base gives とく, a で base gives どく. The request form 〜ておいて likewise becomes 〜といて／〜どいて.
冷蔵庫に牛乳、買っといたよ。
reizōko ni gyūnyū, kattoita yo
I bought milk for the fridge (so we're set).
その資料、読んどくね。
sono shiryō, yondoku ne
I'll go ahead and read that document (for later).
悪いけど、これ皆に伝えといて。
warui kedo, kore minna ni tsutaetoite
Sorry, but go ahead and pass this on to everyone.
The insight: やめておく — deciding in advance not to
Here's the twist that learners almost never predict from "place." The foresight in ておく — setting things up in advance for the best outcome — extends to setting yourself up in advance not to do something. So やめておく doesn't mean "stop placing"; it means "refrain, for the best / I'll pass / better not." It's the grammar of a considered decision to hold back.
今日はお酒、やめとくわ。明日早いから。
kyō wa osake, yametoku wa. ashita hayai kara
I'll pass on drinking today. I've got an early start tomorrow.
その話は、今はやめておこう。
sono hanashi wa, ima wa yamete okō
Let's leave that topic for now (better not get into it).
The logic is the same "arrange things in advance" — only the arrangement is a decision to not act, made deliberately because it's the wiser move. Once you see it as "I'll set myself up to skip this," やめておく stops looking irregular.
Politeness range
ておく scales cleanly across registers by conjugating the おく part: casual 〜とく, plain 〜ておく, polite 〜ておきます, and the request 〜ておいてください / casual 〜といて.
会議の前に、資料は印刷しておきます。
kaigi no mae ni, shiryō wa insatsu shite okimasu
I'll print the materials before the meeting. (polite)
念のため、確認しておいたほうがいいよ。
nen no tame, kakunin shite oita hō ga ii yo
Just to be safe, you'd better check it in advance.
How this differs from English
English has no dedicated grammar for "do it in advance for later." It patches the idea together with adverbials ("beforehand," "ahead of time," "in advance") or the loose phrasal "go ahead and." None of those is obligatory, so English speakers frequently drop the nuance and just say a plain past — "I booked the hotel" — even when the whole point was foresight. Japanese, by contrast, marks that foresight grammatically: 予約しておいた actively says "and I did it so we'd be set." Leaving out ておく isn't wrong, but it flattens a sentence that a native speaker would give the forward-looking shading.
Common mistakes
Using a plain past when the point is advance preparation. Grammatically fine, but it loses the "so we're ready" nuance ておく exists to carry.
❌ 旅行の前に、ホテルを予約した。
ryokō no mae ni, hoteru o yoyaku shita
Merely 'I booked the hotel' — it drops the deliberate 'in advance, so we're set' shading.
✅ 旅行の前に、ホテルを予約しておいた。
ryokō no mae ni, hoteru o yoyaku shite oita
I booked the hotel in advance (so we'd be all set).
Getting the contraction's voicing wrong. A で base contracts to ど, never と.
❌ その本、読んとくね。
sono hon, yontoku ne
Incorrect — 読んでおく has a で base, so it contracts to 読んどく.
✅ その本、読んどくね。
sono hon, yondoku ne
I'll go ahead and read that book (for later).
Writing 置く in kanji. As an auxiliary it's kana; the kanji forces the literal "place."
❌ ビールを冷やして置く。
bīru o hiyashite oku
Reads as 'chill the beer and set it down' — the kanji 置 blocks the 'in advance' meaning.
✅ ビールを冷やしておく。
bīru o hiyashite oku
Chill the beer in advance.
Attaching おく to the wrong form. It needs the て-form, not the dictionary form.
❌ ビールを冷やすおく。
bīru o hiyasu oku
Incorrect — needs the te-form 冷やして, not the dictionary form 冷やす.
✅ ビールを冷やしておく。
bīru o hiyashite oku
Chill the beer ahead of time.
Misreading やめておく as literal "stop placing." It means "refrain / I'll pass," a decision made in advance not to act.
❌ 今日は運動をやめておく。
kyō wa undō o yamete oku
Do NOT read this as 'I stopped placing exercise' — おく is not literal here.
✅ 今日は運動をやめておく。
kyō wa undō o yamete oku
I'll skip exercising today (I've decided it's better not to).
Key takeaways
- 〜ておく (from 置く "place") = do something in advance and leave the result standing for later; also leave a useful state as it is on purpose.
- It grammaticalizes foresight — English has no obligatory equivalent, so don't flatten it into a plain past.
- Spoken Japanese contracts it: 〜てとく and 〜でどく (しとく, 読んどく); request 〜といて／〜どいて.
- やめておく = "refrain / I'll pass" — the "arrange in advance" logic extended to deciding, in advance, not to act.
- Write the auxiliary in kana, and attach it to the て-form.
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Start learning Japanese→Related Topics
- 〜ておく vs 〜てある: Act vs Resulting StateN3 — Two sides of one event — 〜ておく narrates the act of preparing something in advance, while 〜てある describes the state that preparation leaves standing, with a telling を→が particle shift.
- te + Auxiliary Verbs: The Helper FamilyN3 — A map of the 補助動詞 family — a te-form plus a grammaticalized helper (おく, しまう, みる, いく, くる, いる, ある) whose literal meaning has faded into pure aspect or attitude.
- 〜てある: Intentional Resultant StateN4 — How a transitive verb plus ある describes a state someone deliberately set up and left in place — 窓が開けてある 'the window has been opened on purpose' — and why the object takes が.
- 〜てしまう／〜ちゃう: Completion & RegretN3 — How te-form + しまう seals an action as finished — reading it as satisfying completion or as an 'oops, irreversibly' regret, plus the casual 〜ちゃう／〜じゃう contractions and their voicing split.