`loading.js` and [React](/courses/reactjs) `` both provide fallback UI while content is waiting, but they differ mainly in **how much of the interface they control**. ### loading.js A `loading.js` file provides a route-segment-level loading boundary automatically. Example: ```text app/ dashboard/ loading.tsx page.tsx ``` ```tsx export default function Loading() { return ; } ``` This is convenient when most of the changing route can share one loading state. ### Suspense [React](/courses/reactjs) Suspense gives you more precise control inside the page. ```tsx import { Suspense } from 'react'; export default function Dashboard() { return (

Dashboard

}> }>

); } ``` Now the page does not have one all-or-nothing loading state. ### Visual Difference With only route-level loading: ```text Dashboard loading... ``` With granular Suspense boundaries: ```text Dashboard Revenue [Revenue skeleton] Recent Orders [Orders already visible] ``` One slow section does not need to replace every other section with a loading screen. ### When Should You Use loading.js? Use it when you want: - an immediate route-level fallback - a simple loading experience - a page skeleton during navigation ### When Should You Use Suspense Directly? Use Suspense when: - only one section is slow - different areas need different skeletons - you want more granular loading behavior - independent components can become ready separately ### Can You Use Both? Yes. A good page may use: ```text loading.tsx → route-level fallback Suspense → granular loading states inside the page ``` They complement each other rather than competing. ### Interview-Ready Answer `loading.js` automatically creates a Suspense boundary for a route segment and is useful for page-level loading states. React `` gives you finer control around individual components. Use loading.[js](/courses/javascript) for broad route feedback and manual Suspense boundaries when different sections should load independently.