In modern web development, optimising performance and improving search engine ranking (SEO) have become critical factors in evaluating web applications. Angular, a powerful framework for building Single-Page Applications (SPAs), enables developers to create dynamic, interactive experiences. However, SPAs come with inherent limitations, such as delayed initial rendering and poor SEO due to their reliance on Client-Side Rendering (CSR). To mitigate these challenges, Angular Universal enables Server-Side Rendering (SSR), which pre-renders Angular applications on the server and delivers fully populated HTML to the client. This approach significantly enhances performance, SEO, and user experience.

What is Angular Universal?

Angular Universal is a pre-rendering solution that allows Angular applications to support SSR. By default, Angular applications use CSR, where JavaScript executes in the browser to dynamically render content. However, search engine crawlers may struggle with JavaScript-heavy applications, leading to poor indexing (Lyxell, 2023).

With Angular Universal, the application’s HTML is generated on the server, ensuring that search engines and users receive pre-rendered content immediately upon request. This leads to improved SEO and a better First Contentful Paint (FCP), enhancing perceived performance.

How Does Server-Side Rendering (SSR) Work?

In a traditional Client-Side Rendering (CSR) Angular application, the browser downloads JavaScript bundles and executes them to render the page. This results in a delay before users see meaningful content. With SSR, the server pre-renders the HTML before sending it to the client, ensuring a much faster first contentful paint.

For example, consider a simple Angular component that displays user details:

In a CSR setup, the content will only appear once Angular loads and executes the JavaScript on the client. With SSR, this component is rendered on the server and immediately sent to the browser as fully formed HTML.

CSR vs. SSR Comparison

• CSR Approach: The browser downloads JavaScript and renders the component after execution. Users experience a delay before content appears.
• SSR Approach: The server pre-renders the component and sends a fully populated HTML page to the client, improving Largest Contentful Paint (LCP) and SEO.

Benefits of Using Angular Universal

Improved Page Load Speed

With SSR, the Time to First Byte (TTFB) is significantly reduced because the HTML is already generated when the client receives it. This results in better Core Web Vitals, improving user engagement and reducing bounce rates.

Enhanced SEO Optimisation

Search engine crawlers such as Googlebot struggle with JavaScript-heavy pages. Since SSR delivers fully rendered HTML, indexing becomes seamless, leading to improved SEO rankings and better organic reach .

Optimized Social Media Sharing

When a link is shared on platforms like Facebook or Twitter, Open Graph and meta tags are crucial for generating preview snippets. Since SSR pre-renders metadata, social media previews display correctly.

Setting Up Angular Universal

To enable SSR in an Angular project, the first step is to add Angular Universal using the Angular CLI. This can be done with the following command:

This command sets up Angular Universal and modifies the project configuration to support SSR. It also generates a server.ts file, which serves as the entry point for SSR.

Once the setup is complete, the application can be built for SSR using:

This will launch an Express.js server, which pre-renders the application and serves the generated HTML to clients.

Pre-Rendering vs. Dynamic SSR

Another performance optimisation technique is Pre-Rendering, where static HTML files are generated at build time instead of rendering them dynamically per request. This is useful for pages with static content that does not change often (Hulthén, 2024).

For example, a pre-rendering script in Angular Universal might look like this:

This script generates static HTML, which can be cached and served without additional server processing. Pre-rendering is ideal for blog posts, landing pages, and documentation sites, whereas full SSR is better suited for dynamic content such as user dashboards and real-time applications.

When to Use Pre-Rendering vs. SSR?

• Pre-Rendering: Suitable for static pages such as blogs, landing pages, and documentation sites.
• Dynamic SSR: Ideal for user dashboards, real-time applications, and pages with frequently changing content.

Handling API Calls in SSR

One challenge with SSR is handling API calls efficiently. Since data fetching usually happens on the client, SSR requires fetching data on the server before rendering the page.

Consider an Angular service that fetches user data from an API:

When working with SSR, one must ensure that there is available data at the time of page rendering. The TransferState API is an innovative approach that assist to send information between the server and the client so that there are no repeated API calls.

This means that the data fetched on the server is used on the client for optimization and this way there is no unnecessary use of API calls.

Challenges and Considerations

Increased Server Load

SSR requires processing each request on the server, consuming CPU and memory. To optimise this, developers should:

• Implement caching mechanisms (e.g., Redis, Varnish).
• Use Lazy Loading to only load necessary modules.

Limited Access to Browser APIs

Since SSR runs on the server, APIs like window, document, and localStorage are unavailable. To avoid errors, developers can use:

Complexity in State Management

Synchronising state between the server and client can be challenging. Solutions include:

• Using TransferState API for data hydration.
• Leveraging state management libraries like NgRx or Akita to manage shared data efficiently.

Conclusion

Leveraging Angular Universal and Server-Side Rendering (SSR) significantly enhances Angular applications by improving SEO, page load performance, and social media preview generation. SSR ensures that content is immediately available upon request, reducing Time to First Byte (TTFB) and optimising Core Web Vitals.

Reference List

Finckelsen, C., 2025. Environmental Impact Between Client-Side Rendering And Server-Side Rendering In Popular Front-end Frameworks: A comparative analysis.

Hulthén, J., 2024. Streaming Server-Side Rendering: An Empirical Study on Page Performance, Server Load, and User Experience: Comparing streaming Streaming Server-Side Rendering to Standard Server-Side Rendering.

Jartarghar, H.A., Salanke, G.R., AR, A.K., Sharvani, G.S. and Dalali, S., 2022. React apps with Server-Side rendering: Next. js. Journal of Telecommunication, Electronic and Computer Engineering (JTEC), 14(4), pp.25-29.

Lyxell, O., 2023. Server-Side Rendering in React: When Does It Become Beneficial to Your Web Program?.

Meredova, A., 2023. Comparison of server-side rendering capabilities of React and Vue.