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Customizing html.js

Gatsby uses a React component to server render the <head> and other parts of the HTML outside of the core Gatsby application. Gatsby also sets a default value for the <noscript> tag there.

Most sites should use the default html.js shipped with Gatsby. But if you need to customize your site’s html.js, copy the default one into your source tree by running:

cp .cache/default-html.js src/html.js

And then make modifications as needed.

If you need to insert custom html into the <head> or <footer> of each page on your site, you can use html.js.

Required props

Note: the various props that are rendered into pages are required e.g. headComponents, preBodyComponents, body, and postBodyComponents.

Inserting html into the <head>

Anything you render in the html.js component will not be made “live” in the client like other components. If you want to dynamically update your <head> we recommend using React Helmet

If you want to insert custom html into the footer, html.js is the preferred way of doing this. If you’re writing a plugin, consider using the setPostBodyComponents prop in the Gatsby SSR API.

Target container

If you see this error: Uncaught Error: _registerComponent(...): Target container is not a DOM element. it means your html.js is missing the required “target container”. Inside your <body> you must have a div with an id of ___gatsby like:

src/html.js
<div
  key={`body`}
  id="___gatsby"
  dangerouslySetInnerHTML={{ __html: this.props.body }}
/>

Adding custom JavaScript

You can add custom JavaScript to your HTML document by using React’s dangerouslySetInnerHTML attribute.

src/html.js
<script
  dangerouslySetInnerHTML={{
    __html: `
            var name = 'world';
            console.log('Hello ' + name);
        `,
  }}
/>

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