Next.js - optimizations

Next.js - optimizations

Images

<Image>

  • Next.js has a built-in <Image> component
    • Extends <img>
    • .webp or .avif → lossless compression
    • Lazy loading
    • ...

<Image>

<Image>

  1. The image is internal (= included in the build)
    • Location: public
    • Import using ESM import syntax
    • Remember to use the alt tag!
import Image from "next/image";
import mountains from "@/../public/images/mountains-unsplash.jpg";

export default function Home() {
  return (
    <main>  
      <Image src={mountains} alt="image of a beautiful mountain" />
    </main>
  );
}

<Image>

  1. The image is external
    • Refer to a URL
    • Put the domain and protocol in next.config.ts
    • Specify width and height
import Image from "next/image";

export default function Home() {
  return (
    <main>  
      <Image src="https://ahscdn.be/sites/default/files/styles/coursefinder_lg_2x/public/2024-03/ahs_headernew_hires.png?itok=BHQfd4rD" alt="image of a beautiful mountain" />
    </main>
  );
}

<Image>

// next.config.ts
import type { NextConfig } from "next";

const nextConfig: NextConfig = {
  images: {
    remotePatterns: [
      {
        protocol: "https",
        hostname: "ahscdn.be",
      },
    ],
  },
};

export default nextConfig;

<Image>

  • To note:
    • Lazy loading
      • Only in production!
      • Can be disabled with priority
    • fill

Next.js - optimizations

Fonts

Fonts

Fonts

Google Fonts in Next.js

// Example for using Google Fonts with Next.js
import { Geist, Geist_Mono } from "next/font/google";

const geistSans = Geist({
  variable: "--font-geist-sans",
  subsets: ["latin"],
});

const geistMono = Geist_Mono({
  variable: "--font-geist-mono",
  subsets: ["latin"],
});

export default function RootLayout({
  children,
}: Readonly<{
  children: React.ReactNode;
}>) {
  return (
    <html lang="en">
      <body
        className={`${geistSans.variable} ${geistMono.variable} antialiased`}
      >
        {children}
      </body>
    </html>
  );
}

Fonts

  • Specify details to minimize import size
    • subsets (usually: "latin")
    • weight (unless using a variable font)
  • How to apply?
    • Make the variable available on body 
  return (
    <html lang="en">
      <body
        className={`${roboto.variable} antialiased`}
      >
        {children}
      </body>
    </html>
  );

Fonts with Tailwind

To use fonts imported from Google with Tailwind:

/* globals.css */
@import "tailwindcss";

@theme inline {
  --font-roboto: var(--font-roboto);
}

export default function Home() {
  return <p className="font-roboto">Hello there</p>;
}

Fonts with Tailwind

If you only use a single font, you can also use the className property directly

  return (
    <html lang="en">
      <body
        className={`${roboto.className} antialiased`}
      >
        {children}
      </body>
    </html>
  );

Next.js - optimizations

Search Engine Optimization (SEO)

SEO

  • Improve the ranking in search engine results
  • Search engines are not transparent about the criteria

SEO

SEO in Next.js

  • Next.js has a full tutorial on SEO
  • What is relevant for this course:
    • Unique title per page
    • Unique meta description per page

SEO

<html>
  <head>
    <meta name="description" content="Some relevant description of your website, preferably around 150 characters long" />
    <title>My super awesome website</title>
  </head>
  <body>
    <p>Super awesome paragraph!</p>
  </body>
</html>

Search engine results

  • Optimal length:
    • title: 50-60 characters
    • description: around 150 characters

Creating metadata

// Use either one or the other, you can NOT export both
export const metadata: Metadata = {
  title: "My awesome app",
  description: "Generated by create-next-app"
};

export async function generateMetadata(): Promise<Metadata> {
  // ...
}

Creating metadata

When using fetch inside generateMetadata,
the data is automatically cached

import type { Metadata, ResolvingMetadata } from 'next'
 
type Props = {
  params: Promise<{ id: string }>
  searchParams: Promise<{ [key: string]: string | string[] | undefined }>
}
 
export async function generateMetadata(
  { params, searchParams }: Props,
  parent: ResolvingMetadata
): Promise<Metadata> {
  // fetch data
  const product = await fetch(`https://.../${id}`).then((res) => res.json());
}
 
export default function Page({ params, searchParams }: Props) {}
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