All you need to know about Angular Universal

Angular Universal is a technology that renders Angular applications on the server. The angular app gets executed server-side and prepares the page content to be rendered on the client-side. This causes rendering of application faster and the user would be able to see a full-page before it becomes full interactive.

Angular Universal is just a nickname for the Angular server-side rendering. Using Angular CLI we can build the Angular Universal app easily. This will help Angular applications with SEO (search engine optimization), social-media previews, and perceived performance.

SSR angular : How it works

Server-side rendering (SSR) is a process to generate static application pages on the server. Angular Universal is able to generate and serve those SSR pages in response to requests from the web browsers. It will also pre-generate pages as HTML files that you serve later.

Once the page is rendered on the client-side which returned from the server-side. A full angular app rendering will begin using a client-side Angular application. This Angular client App will take over the page, and from there everything is working like a normal single page application (SPA).

All the run time rendering will occur through the client app as usual.

Typical Angular Apps are Single-Page Applications (SPA’s) where rendering occurs on the Browser. This process is able to be referred to client-side rendering (CSR).

Angular universal state transfer API

The TransferState API introduced in Angular v5 can help in this situation. It can transfer data from the server-side of the app to the browser app. For this, the server app will add the data we want to transfer to the HTML page it generates.

 Reasons to use angular universal for app

1. Avail web crawlers through search engine optimization (SEO)
2. Boost performance on mobile and low-powered devices.
3. Show first page quickly with a first-contentful paint (FCP)

Websites like social media apps, eCommerce app, and other applications are rely on web crawlers to index your application content and make that content searchable on the web.

Angular Universal can generate a static version of your app that is easily searchable, linkable, and navigable without JavaScript.

Some devices do not support JavaScript or execute it so slowly that the user experience is too low, in that case, we may need a server-rendered page for a better user experience.

As the page is content to get prepared on the server side so it does not take time while the first load of a web app. So, you will serve a server-side built static page to hold user attention. At the same time, you will load the complete angular app behind it.

Universal web servers

This server responds to application page requests with a static page rendered by the Universal template engine. This server receives and responds to request from the browser.

Angular Universal app can work any web server technology as long as it can call the “renderModule” function of angular universal.

The “renderModule” function takes as input an index.html file, an Angular Module containing angular components, and a route that determines which page to display. Each browser request responded with an appropriate view for a given route.

Angular Universal supports multiple web server technology:

1. Express
2. ASP.Net Core
3. Hapi

Universal bundle

The angular universal app when we implement, it will generate a main.bundle.js file and that is the Universal bundle. The difference between this bundle and the client app bundle is the rendering layer. Here we will use a server-side rendering layer. This layer will return the static page as plain text which will be passed to the client-side to be rendered on the client-side.

Conclusion

As we have seen, the reason for using Angular SSR is to improve the initial performance of the application when the app starts up. Then the page will render a client-side Angular app which will take over the page as usual single page application.

It will benefit search engine optimization. Now it has second priority as Google crawlers are able to indexes well the single page application or javascript pages. But for all other search engines, we need to use server-side rendering.

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I hope that this article helps you to get started with the Angular Universal and that you enjoyed it!