What is the best way to delay the loading of an external CSS file in Next.js version 14?

Question

What is the best way to delay the loading of an external CSS file in Next.js version 14?

To style math equations, I need to load the Katex CSS. The pages that require this styling are not predetermined, as it depends on which users include math in their posts. However, I do know which routes might potentially need it.

For a better understanding, you can visit a page with math here, and one without math here.

Currently, I am loading the CSS using a <link> tag in the header of my root layout, as shown below:

// src/app/layout.jsx

export default async function RootLayout({ children }) {
  return (
    <html suppressHydrationWarning lang="en">
      <head>
        <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="fd969c899885bdcdd3cccbd3c5">[email protected]</a>/dist/katex.min.css" />
      </head>
      <body>
        <main>
         { children }
        </main>
      </body>
    </html>
  )
}

This approach leads to it being categorized as a "render blocking resource," as indicated by my lighthouse report.

https://i.sstatic.net/6KnatOBM.png

If feasible, I would prefer to lazily and dynamically load the CSS based on whether the current page contains math that requires styling.

Despite reviewing the documentation on CSS and lazy loading, such as CSS and lazy loading, I am still uncertain how to achieve this.

css reactjs next.js katex

Answer 1

Answer №1

To dynamically import a library in your code, you can utilize the import function.

Before importing the library, it's advisable to check if the content includes any mathematical equations and then proceed with importing the required library.

if(/* content contains mathematical equation */) {
  const Katex = (await import(/* path to the library */)).default;
}

For further information, you can refer to the documentation here.

In addition, the Head component in Next.js allows you to easily add desired meta tags to your HTML file.

import Head from 'next/head'
 
function IndexPage() {
  return (
    <div>
      <Head>
        <title>My page title</title>
      </Head>
      <p>Hello world!</p>
    </div>
  )
}
 
export default IndexPage

For more details on using the Head component, visit this link.

Answer 2

To dynamically import a library in your code, you can utilize the import function.

Before importing the library, it's advisable to check if the content includes any mathematical equations and then proceed with importing the required library.

if(/* content contains mathematical equation */) {
  const Katex = (await import(/* path to the library */)).default;
}

For further information, you can refer to the documentation here.

In addition, the Head component in Next.js allows you to easily add desired meta tags to your HTML file.

import Head from 'next/head'
 
function IndexPage() {
  return (
    <div>
      <Head>
        <title>My page title</title>
      </Head>
      <p>Hello world!</p>
    </div>
  )
}
 
export default IndexPage

For more details on using the Head component, visit this link.

Answer 3

Answer №2

When it comes to stylesheets without the disabled or media attributes, they are considered render-blocking resources. The process of eliminating them doesn't have a one-size-fits-all solution but rather requires the best-fit approach. I aim to address all your queries related to the What, Why, and How aspects so that you can effectively handle similar scenarios with ease.

Understanding Render-Blocking Resources

The concept of render-blocking URLs has been succinctly explained by Google's documentation:

Lighthouse identifies two types of render-blocking URLs: scripts and stylesheets.

A <script> tag that:

Resides within the <head> section of the document.

Lacks a defer attribute.

Lacks an async attribute.

A
<link rel="stylesheet">
tag that:

Does not contain a disabled attribute. If present, this attribute prevents the browser from downloading the stylesheet.

Does not possess a media attribute tailored to the user's device specifically. Using media="all" is deemed as render-blocking.

Reason Behind Their Rendering Blockage

...

Answer 4

When it comes to stylesheets without the disabled or media attributes, they are considered render-blocking resources. The process of eliminating them doesn't have a one-size-fits-all solution but rather requires the best-fit approach. I aim to address all your queries related to the What, Why, and How aspects so that you can effectively handle similar scenarios with ease.

Understanding Render-Blocking Resources

The concept of render-blocking URLs has been succinctly explained by Google's documentation:

Lighthouse identifies two types of render-blocking URLs: scripts and stylesheets.

A <script> tag that:

Resides within the <head> section of the document.

Lacks a defer attribute.

Lacks an async attribute.

A
<link rel="stylesheet">
tag that:

Does not contain a disabled attribute. If present, this attribute prevents the browser from downloading the stylesheet.

Does not possess a media attribute tailored to the user's device specifically. Using media="all" is deemed as render-blocking.

Reason Behind Their Rendering Blockage

...

Answer 5

Answer №3

Have you taken a look at this documentation ?

npm install katex
npm run build

In your component, make sure to import katex from 'katex';

Next, explore the details at

Answer 6

Have you taken a look at this documentation ?

npm install katex
npm run build

In your component, make sure to import katex from 'katex';

Next, explore the details at

Answer 7

Answer №4

If you're looking for a simple and effective solution, here's one:

Start by creating a local CSS file.

Next, import the external CSS file into the local CSS file.

// externalstyles.css

@import 'https://cdn.jsdelivr.net/npm/example/styles.css'

Then, import or require the local CSS file into your JSX file.

// src/app/layout.jsx

// Option 1: Static Import
import './externalstyles'
import { default as externalstyles} './externalstyles.css'

// With the named import option, you can try injecting the CSS directly in the JSX (untested)

export default async function RootLayout({ children }) {

  if(someCondition)
  {
     // Option 2: Dynamic lazy loaded import with React lazy loader
     const styles = React.lazy(() => import("./externalstyles.css"));

     // Option 3: Dynamic loader with good old require
     const styles = require('./externalstyles.css')
  }


  return (
    <html suppressHydrationWarning lang="en">
      <head>
        <link type="text/css">
          // For the embed import option
          {externalstyles}
        </link>
      </head>
      <body>
        <main>
         { children }
        </main>
      </body>
    </html>
  )
}

Make sure to follow these steps carefully!

Answer 8

If you're looking for a simple and effective solution, here's one:

Start by creating a local CSS file.

Next, import the external CSS file into the local CSS file.

// externalstyles.css

@import 'https://cdn.jsdelivr.net/npm/example/styles.css'

Then, import or require the local CSS file into your JSX file.

// src/app/layout.jsx

// Option 1: Static Import
import './externalstyles'
import { default as externalstyles} './externalstyles.css'

// With the named import option, you can try injecting the CSS directly in the JSX (untested)

export default async function RootLayout({ children }) {

  if(someCondition)
  {
     // Option 2: Dynamic lazy loaded import with React lazy loader
     const styles = React.lazy(() => import("./externalstyles.css"));

     // Option 3: Dynamic loader with good old require
     const styles = require('./externalstyles.css')
  }


  return (
    <html suppressHydrationWarning lang="en">
      <head>
        <link type="text/css">
          // For the embed import option
          {externalstyles}
        </link>
      </head>
      <body>
        <main>
         { children }
        </main>
      </body>
    </html>
  )
}

Make sure to follow these steps carefully!

What is the best way to delay the loading of an external CSS file in Next.js version 14?

Answer №1

Answer №2

Understanding Render-Blocking Resources

Reason Behind Their Rendering Blockage

Answer №3

Answer №4

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