Common Mistakes to Avoid When Using Angular Universal for Server-Side Rendering
Angular Universal Server-Side Rendering SEO Mistakes to avoid TransferState Preboot Optimization Size Testing Web development

José Matos

02 Apr 2023

Common Mistakes to Avoid When Using Angular Universal for Server-Side Rendering

    Common Mistakes to Avoid When Using Angular Universal for Server-Side Rendering

    In today's world of web development, Search Engine Optimization (SEO) is critical for the success of any website or web application. One of the keys to good SEO is ensuring that your website is easily indexable by search engines. Server-Side Rendering (SSR) is a technique for rendering web pages on the server-side before sending them to the client-side. This approach helps search engines to crawl the website and index its content with ease.

    Angular Universal is a framework for server-side rendering of Angular applications. It helps to generate static pages on the server-side before sending the content to the client-side. This technique is not only beneficial for SEO but also enhances the performance and reduces the loading time of your Angular application. However, when working with Angular Universal, there are some common mistakes that developers should avoid to ensure that the application runs smoothly.

    Mistake #1: Using window, document, or navigator in Angular Universal Application

    When working with Server-Side Rendering using Angular Universal, only use browser libraries on the client-side. Libraries like window, document, navigator, and others are not present in the server-side environment, and using them could result in errors. Instead, use Angular's core libraries, such as HttpClient, to fetch data from the server-side.

    Mistake #2: Not Using TransferState or Cached API Response

    When you use SSR, the initial state of your application is stored on the server-side. The state of your application, such as the user's authentication status, data obtained from the API, or any other data, is not present on the client-side. To prevent the application from making API calls on the client-side and improve the user experience, you can store the initial application state using Angular Universal's TransferState API.

    Using the TransferState API, you can cache data obtained from the API during the server-side rendering process. The cached data becomes part of the initial state, which is then passed to the client-side, preventing unnecessary API calls on the client-side. Use this technique to speed up your application's performance and improve the user experience.

    Mistake #3: Not Using Preboot

    Preboot is a library that helps to manage user interactions in Angular, such as button clicks or form submissions. When working with server-side rendering, Preboot helps to synchronize the client-side and server-side events to ensure a seamless user experience. For instance, when a user clicks a button, the Preboot library creates a record of that interaction, which is then replayed on the client-side once the application has finished rendering. This process helps to prevent the application from performing double actions, slow loading times or creating inconsistent user experiences.

    Mistake #4: Not Optimizing the Build for Server-Side Rendering

    When building an Angular application for the server-side, there are several optimizations that you can make to improve its performance. For example, you can use Ahead-of-Time (AoT) compilation, which converts the Angular application code into efficient, low-level code that can be rendered quickly on the client-side. Also, ensure that you are not including any browser-specific libraries or code that are only required for the client-side, as these could slow down your application.

    Mistake #5: Not Considering the Size of the Application

    Angular applications can get quite large, resulting in slower load times for the client. When working with Angular Universal, consider the size of your application and its dependencies. You can use tools like Webpack Bundle Analyzer to analyze the size of your application's bundles and their dependencies. Consider compressing and minifying your assets to reduce their size before sending them to the client-side.

    Mistake #6: Not Testing Server-Side Rendering

    When working with Server-Side Rendering, it is essential to test your application to ensure that everything is working as expected. You can use tools like DevTools or Lighthouse to test your application's performance and SEO. You can also perform manual testing by switching off JavaScript in your browser to see how your application appears to search engines and users who are not using JavaScript. Testing your application regularly can help you avoid issues that occur on the client-side and server-side.


    Angular Universal is a powerful framework for server-side rendering of Angular applications. When working with Angular Universal, ensure that you have a good understanding of the techniques involved and avoid the common mistakes highlighted in this article. Avoiding these mistakes will help you to create faster, more efficient, and SEO-friendly Angular applications.

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