Translation guide
A 'killer app' is a software application so compelling that it drives adoption of the platform it runs on. In Japanese, this is often expressed with the borrowed term キラーアプリ or described with phrases like 決め手となるアプリ.
Referring to a must-have application that makes people want to buy a device or use a service.
Direct loanword from English, widely understood in tech contexts.
このゲームがそのゲーム機のキラーアプリになった。
This game became the killer app for that console.
Descriptive phrase meaning 'the app that is the deciding factor'. Natural when explaining the concept.
この動画編集アプリが、タブレット購入の決め手となるアプリだ。
This video editing app is the killer app that makes people buy the tablet.
Means 'essential app'. Less specific than 'killer app' but conveys must-have status.
スマホユーザーにとって地図アプリは必須アプリだ。
For smartphone users, map apps are a must-have.
キラーアプリ is mainly used in technology, gaming, and business discussions. In everyday conversation, you might explain the concept with a phrase like これがあるから買う (I buy it because it has this).
この端末のキラーアプリは何ですか？
What's the killer app for this device?
Full form of the loanword, slightly more formal or technical.
表計算ソフトはパソコン普及のキラーアプリケーションだった。
Spreadsheet software was the killer application that popularized personal computers.