juniorVue.js
What is the Vue Instance and how is it initialized in Vue 3?
Updated May 4, 2026
Short answer
In Vue 3, the application instance is created using createApp, replacing the Vue 2 new Vue() constructor.
Deep explanation
Vue 3 introduced the concept of an Application Instance to avoid global configuration pollution. In Vue 2, global configurations (like plugins or mixins) affected all Vue instances. With createApp, you create a localized context where you can mount your root component and chain configurations like .use() or .component() specifically for that instance.
Real-world example
Initializing a small widget on a legacy page without affecting other potential Vue instances on the same page.
Common mistakes
- Trying to use `Vue.use()` in Vue 3, which no longer exists as a global method.
Follow-up questions
- Can you mount multiple apps on the same page?