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What’s New in Next.js 15: A Developer’s Guide

Update Dependencies:

In your package.json, remove any references to @next/font. Ensure that your project uses the latest version of Next.js (version 15 or higher).

Test Your Fonts:

Verify that your fonts continue to render correctly after the update.
Check different font weights, styles, and character sets.

Benefits:

Simplified Workflow: No need to manage an additional font package.
Consistent Experience: Leverage the official Next.js font solution.

Conclusion

Next.js 15 is a game-changer for web developers. From lightning-fast build times to cleaner project setup, this version empowers you to create better web applications. Remember to stay up-to-date with the latest features, explore the documentation, and leverage Next.js 15’s enhancements in your projects.

Introduction

Welcome to the exciting world of Next.js 15! In this version, Next.js has undergone significant improvements, making it an even more powerful tool for building modern web applications. Whether you’re a seasoned developer or just getting started, fasten your seatbelt as we explore the latest features and enhancements.

Next.js, a popular React framework, has always been known for its developer-friendly approach, seamless server-side rendering (SSR), and efficient routing. With Next.js 15, the team has raised the bar, addressing pain points and introducing game-changing updates. Let’s dive into what makes this release special:

Faster Build Times

Waiting for builds to complete can be frustrating. Next.js 15 slashes build times dramatically, allowing you to iterate faster and ship code with confidence. We’ll explore how this optimization works and how it impacts your development workflow.

Cleaner UI for create-next-app

Starting a new Next.js project has never been easier. The revamped user interface for creating a new app streamlines the process, guiding you through essential configuration options. Say goodbye to boilerplate setup and hello to productivity!

React 19 Support

As React evolves, so does Next.js. Version 15 embraces React 19 RC, bringing new features and enhancements to both the client and server. We’ll discuss how this compatibility benefits your applications and any considerations you need to keep in mind.

Caching Changes

Next.js 15 introduces changes to caching behavior. Fetch requests, GET route handlers, and client-side router cache now behave differently. We’ll explore these changes and provide practical examples to help you adapt.

Font Package Update

If you’ve been using the @next/font package, there’s a transition to the built-in next/font. Fear not—we’ll guide you through the update process and ensure your fonts continue to shine.

Faster Build Times

What’s Improved?

Next.js 15 introduces a significant enhancement in build times. The build process is now 700 times faster compared to previous versions. This means that when you make changes to your Next.js app and trigger a build, you’ll experience significantly reduced waiting times. Faster builds lead to a more efficient development workflow.

How Does It Work?

The improved build times are achieved through optimizations in the build pipeline. Next.js leverages incremental compilation, smarter caching, and parallel processing to speed up the entire process. When you run next build, the tool intelligently recompiles only the necessary parts of your app, resulting in lightning-fast builds.

Example:

Suppose you have a large Next.js project with multiple pages, components, and styles. In previous versions, a full rebuild would take a considerable amount of time. However, with Next.js 15, the build process is significantly faster. Let’s see a simplified example:

// pages/index.js
import React from 'react';

const HomePage = () => {
  return (
    <div>
      <h1>Welcome to My Next.js App</h1>
      {/* Your content here */}
    </div>
  );
};

export default HomePage;

When you make changes to this page and run next build, Next.js will efficiently update only the modified parts, resulting in a much quicker build

Cleaner UI for create-next-app

What’s Improved?

Creating a new Next.js app is now more straightforward and user-friendly. The updated UI for create-next-app guides you through essential configuration options, making the initial setup a breeze. Whether you’re starting a small project or building a large-scale application, this cleaner interface streamlines the process.

How Does It Work?

When you run the following command in your terminal:

npx create-next-app my-awesome-app

Next.js 15 presents you with a series of prompts. These prompts allow you to customize your app by choosing options like:

TypeScript or JavaScript: You can now easily select TypeScript as your preferred language during project creation.
Styling Solution: Choose between CSS, Sass, or styled-components for styling your components.
ESLint and Prettier Integration: Decide whether to set up ESLint and Prettier for consistent code quality.
Target Environment: Specify whether your app will run in the browser, on the server, or both.

The cleaner UI ensures that you don’t miss any critical settings and provides a smoother experience for developers.

Example:

Let’s say you want to create a new Next.js app with TypeScript and styled-components. Running the npx create-next-app my-awesome-app command will prompt you to choose these options, resulting in a customized project scaffold.

Benefits:

Efficiency: Spend less time configuring your project and more time building features.
Consistency: The guided prompts ensure that your app adheres to best practices from the start.

React 19 Support

What’s New?

Next.js 15 embraces React 19 RC, bringing the latest features and enhancements to your Next.js applications. React 19 introduces concepts like Actions, which allow you to handle asynchronous side effects directly in your components. Let’s dive into the details:

Actions in React 19:

What Are Actions?: Actions are a new way to manage side effects in React components. Instead of relying solely on lifecycle methods or hooks, you can now define actions directly within your component tree.
How Do They Work?: Actions are lightweight functions that encapsulate side effects. You can trigger them from event handlers, lifecycle methods, or other actions. They promote a more declarative and composable approach to handling asynchronous tasks. -Example:

import React, { useState } from 'react';

const MyComponent = () => {
  const [data, setData] = useState(null);

  // Action: Fetch data from an API
  const fetchData = async () => {
    try {
      const response = await fetch('/api/data');
      const result = await response.json();
      setData(result);
    } catch (error) {
      console.error('Error fetching data:', error);
    }
  };

  return (
    <div>
      <button onClick={fetchData}>Fetch Data</button>
      {data && <p>{data.message}</p>}
    </div>
  );
};

export default MyComponent;

Benefits:

Cleaner component code: Actions separate side effects from rendering logic.
Improved testability: You can easily test individual actions in isolation.
Better composability: Actions can be reused across components.

Compatibility Considerations:

Third-Party Libraries: While React 19 brings exciting features, some third-party libraries may not be fully compatible yet. Before upgrading, check if your dependencies support React 19.

Upgrade Tips:

Review Your Components: Identify areas where you can replace lifecycle methods or hooks with actions.
Test Thoroughly: Ensure that your existing components continue to work as expected after the upgrade.
Update Dependencies: If you’re using external libraries, verify their compatibility with React 19.

Caching Changes

What’s Different?

In Next.js 15, caching behavior has undergone some important changes. These changes affect how your app handles fetch requests, GET route handlers, and client-side router cache. Let’s break it down:

Fetch Requests:
- Previous Behavior: Fetch requests were cached by default, which could lead to unexpected results when fetching dynamic data.
- New Behavior: Fetch requests are no longer cached by default. If you want to explicitly cache specific fetch requests, you can pass the cache: 'force-cache' option.
GET Route Handlers:
- Previous Behavior: GET functions in Route Handlers were cached by default, even for dynamic routes.
- New Behavior: GET functions are no longer cached by default. To enable caching for specific routes, you can use a route config option like export dynamic = 'force-static' in your Route Handler file.
Client-side Router Cache:
- Previous Behavior: When navigating between pages using <Link> or useRouter, page segments were reused from the client-side router cache.
- New Behavior: Page segments are no longer reused from the client-side router cache during normal navigation. However, they are still reused during browser backward and forward navigation and for shared layouts. You can control this behavior using the staleTimes config option in your next.config.js.

Example:

Suppose you have an e-commerce site with product pages. Previously, when a user visited different product pages, the client-side router cache would reuse common components. Now, with Next.js 15, you have more control over this behavior.

Benefits:

Fine-Tuned Caching: Customize caching based on your app’s specific needs.
Predictable Behavior: Understand how caching affects your app’s performance.

Font Package Update

What’s Changed?

In Next.js 15, the @next/font package has been deprecated in favor of the built-in next/font. If you were previously using @next/font for managing fonts in your Next.js projects, it’s time to make the transition.

Why the Update?

The move to next/font simplifies font management and aligns with the overall Next.js ecosystem. By using the built-in package, you’ll benefit from better integration and fewer external dependencies.

How to Update:

Replace Imports:

If you were importing fonts using @next/font, update your imports to use next/font/google.

For example:

// Before
import { Roboto } from '@next/font';
// After
import { Roboto } from 'next/font/google';

Update Dependencies:

In your package.json, remove any references to @next/font. Ensure that your project uses the latest version of Next.js (version 15 or higher).