content: [API Reference](https://react.dev/reference/react)
  
  [APIs](https://react.dev/reference/react-dom)
  
  # preinit[Link for this heading]()
  
  ### Note
  
  [React-based frameworks](https://react.dev/learn/start-a-new-react-project) frequently handle resource loading for you, so you might not have to call this API yourself. Consult your framework’s documentation for details.
  
  `preinit` lets you eagerly fetch and evaluate a stylesheet or external script.
  
  ```
  
  preinit("https://example.com/script.js", {as: "script"});
  ```
  
  - [Reference]()
    
    - [`preinit(href, options)`]()
  - [Usage]()
    
    - [Preiniting when rendering]()
    - [Preiniting in an event handler]()
  
  * * *
  
  ## Reference[Link for Reference]()
  
  ### `preinit(href, options)`[Link for this heading]()
  
  To preinit a script or stylesheet, call the `preinit` function from `react-dom`.
  
  ```
  
  import { preinit } from 'react-dom';
  
  
  
  function AppRoot() {
  
    preinit("https://example.com/script.js", {as: "script"});
  
    // ...
  
  }
  ```
  
  [See more examples below.]()
  
  The `preinit` function provides the browser with a hint that it should start downloading and executing the given resource, which can save time. Scripts that you `preinit` are executed when they finish downloading. Stylesheets that you preinit are inserted into the document, which causes them to go into effect right away.
  
  #### Parameters[Link for Parameters]()
  
  - `href`: a string. The URL of the resource you want to download and execute.
  - `options`: an object. It contains the following properties:
    
    - `as`: a required string. The type of resource. Its possible values are `script` and `style`.
    - `precedence`: a string. Required with stylesheets. Says where to insert the stylesheet relative to others. Stylesheets with higher precedence can override those with lower precedence. The possible values are `reset`, `low`, `medium`, `high`.
    - `crossOrigin`: a string. The [CORS policy](https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/crossorigin) to use. Its possible values are `anonymous` and `use-credentials`. It is required when `as` is set to `"fetch"`.
    - `integrity`: a string. A cryptographic hash of the resource, to [verify its authenticity](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity).
    - `nonce`: a string. A cryptographic [nonce to allow the resource](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/nonce) when using a strict Content Security Policy.
    - `fetchPriority`: a string. Suggests a relative priority for fetching the resource. The possible values are `auto` (the default), `high`, and `low`.
  
  #### Returns[Link for Returns]()
  
  `preinit` returns nothing.
  
  #### Caveats[Link for Caveats]()
  
  - Multiple calls to `preinit` with the same `href` have the same effect as a single call.
  - In the browser, you can call `preinit` in any situation: while rendering a component, in an Effect, in an event handler, and so on.
  - In server-side rendering or when rendering Server Components, `preinit` only has an effect if you call it while rendering a component or in an async context originating from rendering a component. Any other calls will be ignored.
  
  * * *
  
  ## Usage[Link for Usage]()
  
  ### Preiniting when rendering[Link for Preiniting when rendering]()
  
  Call `preinit` when rendering a component if you know that it or its children will use a specific resource, and you’re OK with the resource being evaluated and thereby taking effect immediately upon being downloaded.
  
  #### Examples of preiniting[Link for Examples of preiniting]()
  
  1\. Preiniting an external script 2. Preiniting a stylesheet
  
  #### Example 1 of 2: Preiniting an external script[Link for this heading]()
  
  ```
  
  import { preinit } from 'react-dom';
  
  
  
  function AppRoot() {
  
    preinit("https://example.com/script.js", {as: "script"});
  
    return ...;
  
  }
  ```
  
  If you want the browser to download the script but not to execute it right away, use [`preload`](https://react.dev/reference/react-dom/preload) instead. If you want to load an ESM module, use [`preinitModule`](https://react.dev/reference/react-dom/preinitModule).
  
  Next Example
  
  ### Preiniting in an event handler[Link for Preiniting in an event handler]()
  
  Call `preinit` in an event handler before transitioning to a page or state where external resources will be needed. This gets the process started earlier than if you call it during the rendering of the new page or state.
  
  ```
  
  import { preinit } from 'react-dom';
  
  
  
  function CallToAction() {
  
    const onClick = () => {
  
      preinit("https://example.com/wizardStyles.css", {as: "style"});
  
      startWizard();
  
    }
  
    return (
  
      <button onClick={onClick}>Start Wizard</button>
  
    );
  
  }
  ```
  
  [PreviousprefetchDNS](https://react.dev/reference/react-dom/prefetchDNS)
  
  [NextpreinitModule](https://react.dev/reference/react-dom/preinitModule)