Server-Side Rendering in Angular

With fast and efficient web applications, developers are continually seeking ways to enhance performance, user experience, and search engine optimization (SEO). One such strategy is server-side rendering (SSR).

In this article, we will see what SSR is, why it is important, and how to implement it in Angular applications.

What is Server-Side Rendering (SSR)?

In a typical Angular application, the rendering happens on the client-side (i.e., in the browser). When a user visits a webpage, the browser downloads the JavaScript, which then constructs and displays the content. This can cause a delay in rendering the content, particularly for users with slower internet connections or older devices.

Server-side rendering (SSR) involves rendering the initial HTML of a web page on the server instead of in the browser. This pre-rendered HTML is then sent to the browser, allowing the user to see content almost immediately while the JavaScript application loads and becomes interactive in the background. SSR can improve performance and user experience, particularly for users on slower networks. It is also beneficial for SEO because search engines can index the pre-rendered HTML content.

Why Use Server-Side Rendering in Angular?

1. SEO Benefits: Search engines typically struggle to index SPAs that use client-side rendering because the content is dynamically injected by JavaScript. With SSR, search engines receive fully rendered HTML, making it easier to index the content, which can result in better search engine rankings.
2. Faster Initial Page Load: By rendering the HTML on the server and sending it to the client, SSR can drastically reduce the time to first paint (TTFP), improving the perceived performance of the application. Users can view content almost instantly, even before JavaScript has loaded.
3. Better User Experience: Faster page loads translate to a better user experience. Visitors are less likely to leave a page due to long loading times. This is especially important for users with slower devices or connections.
4. Improved Social Media Sharing: Many social media platforms scrape page metadata to display a preview of shared links. SSR ensures that these platforms can access the necessary metadata, improving the presentation of shared content.

SSR in Angular: Angular Universal

Angular provides a powerful tool for implementing server-side rendering through a library known as Angular Universal. Angular Universal allows you to render Angular applications on the server, generating static HTML that is delivered to the client. Angular Universal can be added to any Angular application, providing the benefits of SSR without requiring a complete overhaul of your codebase.

Key Features of Angular Universal:

• Pre-rendering: Angular Universal can pre-render pages and serve them as static HTML, allowing for very fast loading times.
• SEO Optimization: Server-rendered HTML is fully SEO-friendly and can be crawled by search engine bots.
• Improved Performance: Universal reduces the time to interactive (TTI) by serving fully rendered HTML upfront.

Setting Up Server-Side Rendering in Angular

To implement SSR in an Angular application, you need to follow these steps:

Step 1: Install Angular Universal

To begin with, you need to add Angular Universal to your existing Angular project. This can be done using the Angular CLI.

ng add @nguniversal/express-engine

This command adds the necessary Angular Universal packages to your project and configures it with a basic Express server for rendering your Angular application on the server.

Step 2: Modify Your Application for SSR

After adding Angular Universal, the Angular CLI will generate the following files:

1. server.ts: This file contains the code that sets up the Express server and handles server-side rendering.
2. main.server.ts: This file acts as the entry point for the server-side version of your Angular application.
3. tsconfig.server.json: This configuration file specifies the TypeScript settings for building the server-side application.

Additionally, a new output target for the server-side build is created in your angular.json file.

Step 3: Update Angular Configurations

You’ll also need to adjust your build configurations to ensure that both client and server bundles are created. In the angular.json file, you'll find a new server target added under the project. This is used to create the server-side bundle when building your application.

To build the application for SSR, use the following command:

npm run build:ssr

This command will create two sets of bundles: one for the browser and one for the server.

Step 4: Start the Server

Once your project is configured, you can run your application with SSR enabled using the following command:

npm run serve:ssr

This starts up an Express server that renders your Angular application on the server and serves the rendered HTML to the client.

Step 5: Optimize the SSR Implementation

While Angular Universal provides out-of-the-box SSR functionality, there are several optimizations you can make to improve performance:

• Lazy Loading: Use lazy loading for routes and components to reduce the size of the initial HTML payload sent to the client.
• Caching: Implement caching for server-side rendered pages to reduce server load and speed up response times.
• Prefetching and Preloading: Use Angular’s built-in preloading strategies to load critical resources in the background.

Challenges and Considerations

While SSR can bring numerous benefits to Angular applications, there are some challenges and considerations to keep in mind:

1. Increased Complexity: SSR introduces additional complexity to your application. For instance, you’ll need to handle state transfer between the server and client to ensure that both environments have consistent data.
2. Memory Usage: SSR can be more memory-intensive than client-side rendering. You must optimize memory usage on the server to handle multiple simultaneous requests efficiently.
3. Third-Party Libraries: Not all third-party libraries work seamlessly with SSR. Some libraries rely on browser-specific APIs like window or document, which are unavailable on the server.
4. Security: Ensure that sensitive data is not exposed in the server-rendered HTML. Only include data that is safe to be publicly accessible.