| |
| title: getInitialProps |
| description: Fetch dynamic data on the server for your React component with getInitialProps. |
| |
|
|
| > **Good to know**: `getInitialProps` is a legacy API. We recommend using [`getStaticProps`](/docs/pages/building-your-application/data-fetching/get-static-props) or [`getServerSideProps`](/docs/pages/building-your-application/data-fetching/get-server-side-props) instead. |
|
|
| `getInitialProps` is an `async` function that can be added to the default exported React component for the page. It will run on both the server-side and again on the client-side during page transitions. The result of the function will be forwarded to the React component as `props`. |
|
|
| ```tsx filename="pages/index.tsx" switcher |
| import { NextPageContext } from 'next' |
|
|
| Page.getInitialProps = async (ctx: NextPageContext) => { |
| const res = await fetch('https://api.github.com/repos/vercel/next.js') |
| const json = await res.json() |
| return { stars: json.stargazers_count } |
| } |
|
|
| export default function Page({ stars }: { stars: number }) { |
| return stars |
| } |
| ``` |
|
|
| ```jsx filename="pages/index.js" switcher |
| Page.getInitialProps = async (ctx) => { |
| const res = await fetch('https://api.github.com/repos/vercel/next.js') |
| const json = await res.json() |
| return { stars: json.stargazers_count } |
| } |
|
|
| export default function Page({ stars }) { |
| return stars |
| } |
| ``` |
|
|
| > **Good to know**: |
| > |
| > - Data returned from `getInitialProps` is serialized when server rendering. Ensure the returned object from `getInitialProps` is a plain `Object`, and not using `Date`, `Map` or `Set`. |
| > - For the initial page load, `getInitialProps` will run on the server only. `getInitialProps` will then also run on the client when navigating to a different route with the [`next/link`](/docs/pages/api-reference/components/link) component or by using [`next/router`](/docs/pages/api-reference/functions/use-router). |
| > - If `getInitialProps` is used in a custom `_app.js`, and the page being navigated to is using `getServerSideProps`, then `getInitialProps` will also run on the server. |
|
|
| ## Context Object |
|
|
| `getInitialProps` receives a single argument called `context`, which is an object with the following properties: |
|
|
| | Name | Description | |
| | |
| | `pathname` | Current route, the path of the page in `/pages` | |
| | `query` | Query string of the URL, parsed as an object | |
| | `asPath` | `String` of the actual path (including the query) shown in the browser | |
| | `req` | [HTTP request object](https://nodejs.org/api/http.html#http_class_http_incomingmessage) (server only) | |
| | `res` | [HTTP response object](https://nodejs.org/api/http.html#http_class_http_serverresponse) (server only) | |
| | `err` | Error object if any error is encountered during the rendering | |
|
|
| ## Caveats |
|
|
| - `getInitialProps` can only be used in `pages/` top level files, and not in nested components. To have nested data fetching at the component level, consider exploring the [App Router](/docs/app/getting-started/fetching-data). |
| - Regardless of whether your route is static or dynamic, any data returned from `getInitialProps` as `props` will be able to be examined on the client-side in the initial HTML. This is to allow the page to be [hydrated](https://react.dev/reference/react-dom/hydrate) correctly. Make sure that you don't pass any sensitive information that shouldn't be available on the client in `props`. |
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