AI translation is good enough to make your app readable in Japanese. It is not yet good enough to make it sound like a Japanese product.
Japanese users notice the difference in seconds. A playful error message translated word for word, a button that uses a school word, a "you" in every sentence — each one is small, but together they say "this wasn't made for Japan". And people trust that product a little less, especially at checkout.
I'm a native Japanese developer and I build checkouts for Japanese online stores. Below are 12 UI strings where machine translation typically goes wrong, what a Japanese product would say instead, and the rules behind them, so you can fix your own text too.
12 strings that give it away
| English | Typical AI translation (avoid) | Natural Japanese | Why |
|---|---|---|---|
| Oops! Something went wrong. | おっと！何かがうまくいきませんでした。 | エラーが発生しました。 | Playful errors don't translate. State it plainly and politely. |
| Learn more | もっと学ぶ | 詳しく見る | もっと学ぶ means "study more". |
| Submit | 提出 | 送信 | 提出 is for homework and official documents. Forms use 送信. |
| Checkout | チェックアウト | ご購入手続きへ | チェックアウト sounds like leaving a hotel. |
| Saved! | 保存されました！ | 保存しました | Use the active past form, not the passive. |
| Delete this item? | このアイテムを削除？ | この項目を削除しますか？ | A bare noun + "?" looks broken. End with 〜しますか？ |
| Are you sure? | 本当ですか？ | よろしいですか？ | 本当ですか？ means "Really? Is that true?" |
| Forgot your password? | パスワードを忘れましたか？ | パスワードをお忘れの方 | The question sounds like an accusation. |
| Remember me | 私を覚えて | ログイン状態を保持する | The literal version reads like a song lyric. |
| Your card was declined. | あなたのカードは拒否されました。 | カードがご利用いただけませんでした。 | 拒否 (rejected) is harsh for a payment problem. |
| First name | 最初の名前 | 名 | In Japan the family name comes first, so "first name" is the second field. |
| Hi Taro, (email) | こんにちは太郎、 | 山田 太郎 様 | Customers are addressed by family or full name + 様. |
None of the "avoid" versions are wrong Japanese, exactly. They are just not what a Japanese product would say, and that's what users pick up on.
The 6 rules behind them
1. Buttons are short nouns.
Japanese buttons usually read like labels: 保存 (save), 送信 (send), 変更を保存 (save changes). A full verb like 保存する on every button feels wordy. (A few fixed phrases are exceptions: カートに入れる for Add to cart is the norm on Japanese shops.)
2. Sentences end in です／ます.
Messages, errors and confirmations are polite sentences. AI translations often mix in the plain form (だ／である), which feels cold or like a technical manual.
3. Drop "you".
English UI says your everywhere: your cart, your account, your changes. Japanese UI almost never says あなたの. It sounds distant, sometimes even rude. Just drop it: カートに商品はありません (there are no items in the cart).
4. Success messages use the active past.
保存しました (I saved it), 送信しました (sent). The passive 保存されました is a classic machine-translation tell.
5. Pick one word and stick to it.
カート or 買い物かご. ログイン or サインイン. 設定, never also セッティング. Mixing terms is one of the fastest ways to look machine-translated, because each string was translated on its own.
6. Follow the Japanese order.
Family name first, then furigana (the reading in katakana). Postal code → prefecture → city. Year → month → day. 24-hour time for deadlines and delivery slots. Prices in yen with no decimals and tax included (¥1,500 or 1,500円).
A quick way to check your own app
- Export your Japanese strings (CSV, JSON, .strings, whatever you use).
- Search for あなた. Most of them can go.
- Search for されました. Most success messages should be しました.
- Look at every string that ends in ？ — does it end in a verb (しますか？) or a bare noun?
- List your katakana words and check for duplicates (ユーザー／ユーザ, ログイン／サインイン).
- Read your error messages out loud. If one sounds like a joke or an accusation, rewrite it.
This won't catch everything, but it catches the most visible problems in about 15 minutes.
If you want the full list
I put 225 of these together in a Japanese UI Phrasebook: sign-up, navigation, buttons, Japan-specific form fields, errors, confirmations, cart and checkout, payment (including konbini payment), shipping time slots, subscriptions, settings, email subjects and legal pages. Each string has the English, the natural Japanese, the version to avoid, and why. It comes as a PDF, CSV and JSON, including a flat ja.json you can drop into your i18n setup.
- Free sample (36 strings): Japanese UI Phrasebook — Free Sample
- Full version (225 strings): Japanese UI Phrasebook
And if you'd rather have a native speaker read your actual text, I also proofread app and game Japanese on Fiverr.
For forms specifically (name order, furigana, postal codes), see my earlier post: How to Build a Checkout Form That Works in Japan.
