What are the main Angular 19 updates? - Part 1

Angular v19 introduces notable additions and enhancements including hot module replacement, time picker component, and standalone defaults.

Here is the Angular 19 features list:

•    Incremental Hydration
•    Standalone Defaults 
•    Route-level Render Mode
•    Hot Module Replacement
•    Linked Signals
•    Event Replay
•    Modernizing Code with Language Service    
•    State of Zoneless
•    State of Testing Tooling
•    Security with Google
•    Resource
•    Time Picker Component
•    Two-dimensional Drag and Drop

Incremental hydration (Developer preview)- Angular 19 supports incremental hydration (activating a server-side rendered HTML page on the client), giving better control

• Traditional Angular hydrates the entire application in one go after receiving the HTML. Because the entire website must be bootstrapped at once, making it interactive might be slow, especially if the application is large or sophisticated. Incremental incremental hydration improves client-side JavaScript loading and execution to boost server-side rendered application performance. This feature bootstraps components of the program progressively to speed up page interaction. Smaller application pieces are hydrated as needed by Angular.

 

• How? With incremental hydration, Angular divides the app into “hydration zones” or “hydration chunks.” Angular will hydrate the visible elements of the page first after receiving the server-rendered HTML. After those are interactive, Angular will background-hydrate the rest of the page. Angular 17 introduces @defer syntax to identify template portions for incremental hydration, allowing Angular to lazy load and hydrate them only when certain triggers occur.

@defer (hydrate on viewport) {
<your-component />
}

Standalone by default
Standalone components were introduced in v14. Angular 19, standalone components are now the default way to define and build Angular components. This change simplifies the metadata of all your standalone components, directives, and pipes. Even the Angular docs now encourage new developers to choose ‘Standalone first’ so they can start right from the beginning.

• Why standalone?
  Simplifies the learning curve for new developers.
  Encourages better modularization of codebases.
  Reduces boilerplate (the standardised and repetitive code developers have historically had to write to create and control Angular applications, especially with regard to modules, components, and routing), leading to faster development cycles.

 

Render Mode at Route Level 

in Earlier versions, Angular would by default render all the parametrised routes in your app and prerender all routes without parameters when you enabled server-side rendering in your application. But version 19 adds ServerRoute, a tool that lets you more finely customise how specific routes in your Angular application render. 

This interface lets you indicate whether each route should be processed on the server side, pre-rendered on the server, or rendered on the client side, hence allowing you to fine-tune the rendering behaviour.

Set Routes at TS level

export const serverRouteConfig: ServerRoute[] = [

 { path: '/login', mode: 'server' },  // Render login route on the server for optimal security
 { path: '/dashboard', mode: 'client' }, // Render dashboard route on the client for a more dynamic experience
 { path: '/**', mode: 'prerender' }, // Prerender all other routes for initial load speed
];

Angular 19 new features list will offer users innovation and efficiency.

Hot Module Replacement (HMR) and time picker Tool

• Without a page or browser refresh, the HMR function lets developers make quick changes and update the design or template of a web application. Therefore, there will be no state loss, which will improve developer experience and speed up turnaround time. Keeping application state that would otherwise be lost on a complete reload 
• Updating only what has changed Instantly changing the browser when CSS/JS in the source code changes. HMR helps in the following ways: 
  • You save the file and correct the button's code. Angular sees the change and modifies just the button component. 
  • The remainder of the application stays the same, including the list of tasks you have previously added.
• Enable HMR in Angular 19

Serve with HMR flag
ng serve --hmr

OR

 

Through Environment Configuration (Optional): Especially for production vs. development settings, this offers more control. edit environment.ts

For Development

export const environment = {
 production: false,
 hmr: false // HMR disabled by default in dev
};

For Production

export const environment = {
 production: true,
 hmr: false // HMR always disabled in production
};

Check in main.ts

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { AppModule } from './app/app.module';
import { environment } from './environments/environment';

if (environment.hmr) {  // Check if HMR is enabled
  if (module['hot']) {
    module['hot'].accept();
  } else {
    console.error('HMR is not enabled for webpack-dev-server!');
    throw new Error('HMR is not enabled for webpack-dev-server!');
  }
}
platformBrowserDynamic().bootstrapModule(AppModule)
  .catch(err => console.error(err));

For other features see What are the main Angular 19 updates? - Part 2