Accessibility in Angular link

The web is used by a wide variety of people, including those who have visual or motor impairments. A variety of assistive technologies are available that make it much easier for these groups to interact with web-based software applications. Also, designing an application to be more accessible generally improves the user experience for all users.

For an in-depth introduction to issues and techniques for designing accessible applications, see the Accessibility section of the Google's Web Fundamentals.

This page discusses best practices for designing Angular applications that work well for all users, including those who rely on assistive technologies.

Accessibility attributes link

Building accessible web experience often involves setting Accessible Rich Internet Applications (ARIA) attributes to provide semantic meaning where it might otherwise be missing. Use attribute binding template syntax to control the values of accessibility-related attributes.

When binding to ARIA attributes in Angular, you must use the attr. prefix. The ARIA specification depends specifically on HTML attributes rather than properties of DOM elements.

      
        content_copy
      
      <!-- Use attr. when binding to an ARIA attribute -->
<button [attr.aria-label]="myActionLabel">…</button>
    

      
        content_copy
      
      <!-- Static ARIA attributes require no extra syntax -->
<button aria-label="Save document">…</button>
    

Angular UI components link

The Angular Material library, which is maintained by the Angular team, is a suite of reusable UI components that aims to be fully accessible. The Component Development Kit (CDK) includes the a11y package that provides tools to support various areas of accessibility. For example:

• LiveAnnouncer is used to announce messages for screen-reader users using an aria-live region. See the W3C documentation for more information on aria-live regions.

• The cdkTrapFocus directive traps Tab-key focus within an element. Use it to create accessible experience for components such as modal dialogs, where focus must be constrained.

For full details of these and other tools, see the Angular CDK accessibility overview.

Augmenting native elements link

Native HTML elements capture several standard interaction patterns that are important to accessibility. When authoring Angular components, you should re-use these native elements directly when possible, rather than re-implementing well-supported behaviors.

For example, instead of creating a custom element for a new variety of button, create a component that uses an attribute selector with a native <button> element. This most commonly applies to <button> and <a> , but can be used with many other types of element.

You can see examples of this pattern in Angular Material: MatButton , MatTabNav , and MatTable .

Using containers for native elements link

Sometimes using the appropriate native element requires a container element. For example, the native <input> element cannot have children, so any custom text entry components need to wrap an <input> with extra elements. By just including <input> in your custom component's template, it's impossible for your component's users to set arbitrary properties and attributes to the <input> element. Instead, create a container component that uses content projection to include the native control in the component's API.

You can see MatFormField as an example of this pattern.

Case study: Building a custom progress bar link

The following example shows how to make a progress bar accessible by using host binding to control accessibility-related attributes.

• The component defines an accessibility-enabled element with both the standard HTML attribute role , and ARIA attributes. The ARIA attribute aria-valuenow is bound to the user's input.

  src/app/progress-bar.component.ts

        
          content_copy
        
        import { Component, Input } from '@angular/core';
  
  /**
   * Example progressbar component.
   */
  @Component({
    selector: 'app-example-progressbar',
    template: '<div class="bar" [style.width.%]="value"></div>',
    styleUrls: ['./progress-bar.component.css'],
    host: {
      // Sets the role for this component to "progressbar"
      role: 'progressbar',
  
      // Sets the minimum and maximum values for the progressbar role.
      'aria-valuemin': '0',
      'aria-valuemax': '100',
  
      // Binding that updates the current value of the progressbar.
      '[attr.aria-valuenow]': 'value',
    }
  })
  export class ExampleProgressbarComponent  {
    /** Current value of the progressbar. */
    @Input() value = 0;
  }
      

• In the template, the aria-label attribute ensures that the control is accessible to screen readers.

  src/app/app.component.html

        
          content_copy
        
        <label>
    Enter an example progress value
    <input type="number" min="0" max="100"
        [value]="progress" (input)="setProgress($event)">
  </label>
  
  <!-- The user of the progressbar sets an aria-label to communicate what the progress means. -->
  <app-example-progressbar [value]="progress" aria-label="Example of a progress bar">
  </app-example-progressbar>
      

Routing link

Focus management after navigation link

Tracking and controlling focus in a UI is an important consideration in designing for accessibility. When using Angular routing, you should decide where page focus goes upon navigation.

To avoid relying solely on visual cues, you need to make sure your routing code updates focus after page navigation. Use the NavigationEnd event from the Router service to know when to update focus.

The following example shows how to find and focus the main content header in the DOM after navigation.

      
        content_copy
      
      router.events.pipe(filter(e => e instanceof NavigationEnd)).subscribe(() => {
  const mainHeader = document.querySelector('#main-content-header')
  if (mainHeader) {
    mainHeader.focus();
  }
});
    

In a real application, the element that receives focus depends on your specific application structure and layout. The focused element should put users in a position to immediately move into the main content that has just been routed into view. You should avoid situations where focus returns to the body element after a route change.

Active links identification link

CSS classes applied to active RouterLink elements, such as RouterLinkActive , provide a visual cue to identify the active link. Unfortunately, a visual cue doesn't help blind or visually impaired users. Applying the aria-current attribute to the element can help identify the active link. For more information, see Mozilla Developer Network (MDN) aria-current).

The RouterLinkActive directive provides the ariaCurrentWhenActive input which sets the aria-current to a specified value when the link becomes active.

The following example shows how to apply the active-page class to active links as well as setting their aria-current attribute to "page" when they are active:

      
        content_copy
      
      <nav>
  <a routerLink="home"
     routerLinkActive="active-page"
     ariaCurrentWhenActive="page">
    Home
  </a>
  <a routerLink="about"
     routerLinkActive="active-page"
     ariaCurrentWhenActive="page">
    About
  </a>
  <a routerLink="shop"
     routerLinkActive="active-page"
     ariaCurrentWhenActive="page">
    Shop
  </a>
</nav>
    

More information link

• Accessibility - Google Web Fundamentals
• ARIA specification and authoring practices
• Material Design - Accessibility
• Smashing Magazine
• Inclusive Components
• Accessibility Resources and Code Examples
• W3C - Web Accessibility Initiative
• Rob Dodson A11ycasts
• Angular ESLint provides linting rules that can help you make sure your code meets accessibility standards.

Books

• "A Web for Everyone: Designing Accessible User Experiences," Sarah Horton and Whitney Quesenbery
• "Inclusive Design Patterns," Heydon Pickering

AngularJS to Angular concepts: Quick reference link

Angular is the name for the Angular of today and tomorrow.

AngularJS is the name for all v1.x versions of Angular.

This guide helps you transition from AngularJS to Angular by mapping AngularJS syntax to the corresponding Angular syntax.

See the Angular syntax in this live example / download example .

Template basics link

Templates are the user-facing part of an Angular application and are written in HTML. The following table lists some of the key AngularJS template features with their corresponding Angular template syntax.

Bindings / interpolation → bindings / interpolation link

      
      Your favorite hero is: {{vm.favoriteHero}}
    

      
      Your favorite hero is: {{favoriteHero}}
    

Filters → pipes link

      
      <td> 
  {{movie.title | uppercase}} 
</td>
    

      
      <td>{{movie.title | uppercase}}</td>
    

Local variables → input variables link

      
      <tr ng-repeat="movie in vm.movies"> 
  <td> 
    {{movie.title}} 
  </td> 
</tr>
    

      
      <tr *ngFor="let movie of movies">
  <td>{{movie.title}}</td>
</tr>
    

Template directives link

AngularJS provides more than seventy built-in directives for templates. Many of them are not needed in Angular because of its more capable and expressive binding system. The following are some of the key AngularJS built-in directives and their equivalents in Angular.

ng-app → bootstrapping link

      
      <body ng-app="movieHunter">
    

      
      import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';

platformBrowserDynamic().bootstrapModule(AppModule)
  .catch(err => console.error(err));
    

      
      import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent } from './app.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }
    

ng-class → ngClass link

      
      <div ng-class="{active: isActive}"> 
<div ng-class="{active: isActive, shazam: isImportant}">
    

      
      <div [ngClass]="{'active': isActive}">
<div [ngClass]="{'active': isActive,
                 'shazam': isImportant}">
<div [class.active]="isActive">
    

ng-click → Bind to the click event link

      
      <button ng-click="vm.toggleImage()"> 
<button ng-click="vm.toggleImage($event)">
    

      
      <button type="button" (click)="toggleImage()">
<button type="button" (click)="toggleImage($event)">
    

ng-controller → component decorator link

      
      <div ng-controller="MovieListCtrl as vm">
    

      
      @Component({
  selector: 'app-movie-list',
  templateUrl: './movie-list.component.html',
  styleUrls: [ './movie-list.component.css' ],
})
    

ng-hide → Bind to the hidden property link

ng-href → Bind to the href property link

      
      <a ng-href="{{ angularDocsUrl }}"> 
  Angular Docs 
</a>
    

      
      <a ng-href="#{{ moviesHash }}"> 
  Movies 
</a>
    

      
      <a [href]="angularDocsUrl">Angular Docs</a>
    

      
      <a [routerLink]="['/movies']">Movies</a>
    

ng-if → *ngIf link

      
      <table ng-if="movies.length">
    

      
      <table *ngIf="movies.length">
    

ng-model → ngModel link

      
      <input ng-model="vm.favoriteHero" />
    

      
      <input [(ngModel)]="favoriteHero" />
    

ng-repeat → *ngFor link

      
      <tr ng-repeat="movie in vm.movies">
    

      
      <tr *ngFor="let movie of movies">
    

ng-show → Bind to the hidden property link

      
      <h3 ng-show="vm.favoriteHero"> 
  Your favorite hero is: {{vm.favoriteHero}} 
</h3>
    

      
      <h3 [hidden]="!favoriteHero">
  Your favorite hero is: {{favoriteHero}}
</h3>
    

ng-src → Bind to the src property link

      
      <img ng-src="{{movie.imageurl}}">
    

      
      <img [src]="movie.imageurl" [alt]="movie.title">
    

ng-style → ngStyle link

      
      <div ng-style="{color: colorPreference}">
    

      
      <div [ngStyle]="{'color': colorPreference}">
<div [style.color]="colorPreference">
    

ng-switch → ngSwitch link

      
      <div ng-switch="vm.favoriteHero && vm.checkMovieHero(vm.favoriteHero)"> 
  <div ng-switch-when="true"> 
    Excellent choice. 
  </div> 
  <div ng-switch-when="false"> 
    No movie, sorry. 
  </div> 
  <div ng-switch-default> 
    Please enter your favorite hero. 
  </div> 
</div>
    

      
      <span [ngSwitch]="favoriteHero &&
               checkMovieHero(favoriteHero)">
  <p *ngSwitchCase="true">
    Excellent choice!
  </p>
  <p *ngSwitchCase="false">
    No movie, sorry!
  </p>
  <p *ngSwitchDefault>
    Please enter your favorite hero.
  </p>
</span>
    

Filters / pipes link

Angular pipes provide formatting and transformation for data in the template, like AngularJS filters . Many of the built-in filters in AngularJS have corresponding pipes in Angular. For more information on pipes, see Pipes.

currency → currency link

      
      <td> 
  {{movie.price | currency}} 
</td>
    

      
      <td>{{movie.price | currency:'USD':true}}</td>
    

date → date link

      
      <td> 
  {{movie.releaseDate | date}} 
</td>
    

      
      <td>{{movie.releaseDate | date}}</td>
    

filter → none link

      
      <tr ng-repeat="movie in movieList | filter: {title:listFilter}">
    

json → json link

      
      <pre> 
  {{movie | json}} 
</pre>
    

      
      <pre>{{movie | json}}</pre>
    

limitTo → slice link

      
      <tr ng-repeat="movie in movieList | limitTo:2:0">
    

      
      <tr *ngFor="let movie of movies | slice:0:2">
    

lowercase → lowercase link

      
      <td> 
  {{movie.title | lowercase}} 
</td>
    

      
      <td>{{movie.title | lowercase}}</td>
    

number → number link

      
      <td> 
  {{movie.starRating | number}} 
</td>
    

      
      <td>{{movie.starRating | number}}</td>
<td>{{movie.starRating | number:'1.1-2'}}</td>
<td>{{movie.approvalRating | percent: '1.0-2'}}</td>
    

orderBy → none link

      
      <tr ng-repeat="movie in movieList | orderBy : 'title'">
    

Modules / controllers / components link

In both AngularJS and Angular, modules help you organize your application into cohesive blocks of features.

In AngularJS, you write the code that provides the model and the methods for the view in a controller . In Angular, you build a component .

Because much AngularJS code is in JavaScript, JavaScript code is shown in the AngularJS column. The Angular code is shown using TypeScript.

Immediately invoked function expression (IIFE) → none link

      
      ( 
  function () { 
    … 
  }() 
);
    

Angular modules → NgModules link

      
      angular .module( 
  "movieHunter", 
  [ 
    "ngRoute" 
  ] 
);
    

      
      import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent } from './app.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }
    

Controller registration → component decorator link

      
      angular .module( 
  "movieHunter" 
) .controller( 
  "MovieListCtrl", 
  [ 
    "movieService", 
    MovieListCtrl 
  ] 
);
    

      
      @Component({
  selector: 'app-movie-list',
  templateUrl: './movie-list.component.html',
  styleUrls: [ './movie-list.component.css' ],
})
    

Controller function → component class link

      
      function MovieListCtrl(movieService) { 
}
    

      
      export class MovieListComponent {
}
    

Dependency injection → dependency injection link

      
      MovieListCtrl.$inject = [ 
  'MovieService' 
]; 
function MovieListCtrl(movieService) { 
}
    

      
      constructor(movieService: MovieService) {
}
    

Style sheets link

Style sheets give your application a nice look. In AngularJS, you specify the style sheets for your entire application. As the application grows over time, the styles for the many parts of the application merge, which can cause unexpected results. In Angular, you can still define style sheets for your entire application. Now you can also encapsulate a style sheet within a specific component.

Link tag → styles configuration or styleUrls link

      
      <link href="styles.css" 
      rel="stylesheet" />
    

      
      "styles": [
  "styles.css"
],
    

      
      styleUrls: [ './movie-list.component.css' ],
    

Angular compiler options link

When you use ahead-of-time compilation (AOT), you can control how your application is compiled by specifying template compiler options in the TypeScript configuration file.

The template options object, angularCompilerOptions , is a sibling to the compilerOptions object that supplies standard options to the TypeScript compiler.

      
        content_copy
      
      {
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    // ...
  },
  "angularCompilerOptions": {
    "enableI18nLegacyMessageIdFormat": false,
    "strictInjectionParameters": true,
    // ...
  }
}
    

Configuration inheritance with extends link

Like the TypeScript compiler, the Angular AOT compiler also supports extends in the angularCompilerOptions section of the TypeScript configuration file. The extends property is at the top level, parallel to compilerOptions and angularCompilerOptions .

A TypeScript configuration can inherit settings from another file using the extends property. The configuration options from the base file are loaded first, then overridden by those in the inheriting configuration file.

For example:

      
        content_copy
      
      {
    "extends": "./tsconfig.json",
    "compilerOptions": {
      "outDir": "./out-tsc/app",
    // ...
    "angularCompilerOptions": {
      "strictTemplates": true,
      "preserveWhitespaces": true,
      // ...
    }
  }
    

For more information, see the TypeScript Handbook.

Template options link

The following options are available for configuring the AOT template compiler.

allowEmptyCodegenFiles link

When true , create all possible files even if they are empty. Default is false . Used by the Bazel build rules to simplify how Bazel rules track file dependencies. Do not use this option outside of the Bazel rules.

annotationsAs link

Modifies how Angular-specific annotations are emitted to improve tree-shaking. Non-Angular annotations are not affected. One of static fields or decorators . The default value is static fields .

• By default, the compiler replaces decorators with a static field in the class, which allows advanced tree-shakers like Closure compiler to remove unused classes

• The decorators value leaves the decorators in place, which makes compilation faster. TypeScript emits calls to the __decorate helper. Use --emitDecoratorMetadata for runtime reflection.

  NOTE :
  That the resulting code cannot tree-shake properly.

annotateForClosureCompiler link

When true , use Tsickle to annotate the emitted JavaScript with JSDoc comments needed by the Closure Compiler. Default is false .

compilationMode link

Specifies the compilation mode to use. The following modes are available:

The default value is 'full' .

disableExpressionLowering link

When true , the default, transforms code that is or could be used in an annotation, to allow it to be imported from template factory modules. See metadata rewriting for more information.

When false , disables this rewriting, requiring the rewriting to be done manually.

disableTypeScriptVersionCheck link

When true , the compiler does not look at the TypeScript version and does not report an error when an unsupported version of TypeScript is used. Not recommended, as unsupported versions of TypeScript might have undefined behavior. Default is false .

enableI18nLegacyMessageIdFormat link

Instructs the Angular template compiler to create legacy ids for messages that are tagged in templates by the i18n attribute. See Mark text for translations for more information about marking messages for localization.

Set this option to false unless your project relies upon translations that were created earlier using legacy IDs. Default is true .

The pre-Ivy message extraction tooling created a variety of legacy formats for extracted message IDs. These message formats have some issues, such as whitespace handling and reliance upon information inside the original HTML of a template.

The new message format is more resilient to whitespace changes, is the same across all translation file formats, and can be created directly from calls to $localize . This allows $localize messages in application code to use the same ID as identical i18n messages in component templates.

enableResourceInlining link

When true , replaces the templateUrl and styleUrls properties in all @Component decorators with inline content in the template and styles properties.

When enabled, the .js output of ngc does not include any lazy-loaded template or style URLs.

For library projects created with the Angular CLI, the development configuration default is true .

enableLegacyTemplate link

When true , enables the deprecated <template> element in place of <ng-template> . Default is false . Might be required by some third-party Angular libraries.

flatModuleId link

The module ID to use for importing a flat module (when flatModuleOutFile is true ). References created by the template compiler use this module name when importing symbols from the flat module. Ignored if flatModuleOutFile is false .

flatModuleOutFile link

When true , generates a flat module index of the given filename and the corresponding flat module metadata. Use to create flat modules that are packaged similarly to @angular/core and @angular/common . When this option is used, the package.json for the library should refer to the created flat module index instead of the library index file.

Produces only one .metadata.json file, which contains all the metadata necessary for symbols exported from the library index. In the created .ngfactory.js files, the flat module index is used to import symbols. Symbols that include both the public API from the library index as well as shrouded internal symbols.

By default the .ts file supplied in the files field is assumed to be the library index. If more than one .ts file is specified, libraryIndex is used to select the file to use. If more than one .ts file is supplied without a libraryIndex , an error is produced.

A flat module index .d.ts and .js is created with the given flatModuleOutFile name in the same location as the library index .d.ts file.

For example, if a library uses the public_api.ts file as the library index of the module, the tsconfig.json files field would be ["public_api.ts"] . The flatModuleOutFile option could then be set, for example, to "index.js" , which produces index.d.ts and index.metadata.json files. The module field of the library's package.json would be "index.js" and the typings field would be "index.d.ts" .

fullTemplateTypeCheck link

When true , the recommended value, enables the binding expression validation phase of the template compiler. This phase uses TypeScript to verify binding expressions. For more information, see Template type checking.

Default is false , but when you use the Angular CLI command ng new --strict , it is set to true in the new project's configuration.

generateCodeForLibraries link

When true , creates factory files ( .ngfactory.js and .ngstyle.js ) for .d.ts files with a corresponding .metadata.json file. The default value is true .

When false , factory files are created only for .ts files. Do this when using factory summaries.

preserveWhitespaces link

When false , the default, removes blank text nodes from compiled templates, which results in smaller emitted template factory modules. Set to true to preserve blank text nodes.

skipMetadataEmit link

When true , does not produce .metadata.json files. Default is false .

The .metadata.json files contain information needed by the template compiler from a .ts file that is not included in the .d.ts file produced by the TypeScript compiler. This information includes, for example, the content of annotations, such as a component's template, which TypeScript emits to the .js file but not to the .d.ts file.

You can set to true when using factory summaries, because the factory summaries include a copy of the information that is in the .metadata.json file.

Set to true if you are using TypeScript's --outFile option, because the metadata files are not valid for this style of TypeScript output. The Angular community does not recommend using --outFile with Angular. Use a bundler, such as webpack, instead.

skipTemplateCodegen link

When true , does not emit .ngfactory.js and .ngstyle.js files. This turns off most of the template compiler and disables the reporting of template diagnostics.

Can be used to instruct the template compiler to produce .metadata.json files for distribution with an npm package. This avoids the production of .ngfactory.js and .ngstyle.js files that cannot be distributed to npm .

For library projects created with the Angular CLI, the development configuration default is true .

strictMetadataEmit link

When true , reports an error to the .metadata.json file if "skipMetadataEmit" is false . Default is false . Use only when "skipMetadataEmit" is false and "skipTemplateCodegen" is true .

This option is intended to verify the .metadata.json files emitted for bundling with an npm package. The validation is strict and can emit errors for metadata that would never produce an error when used by the template compiler. You can choose to suppress the error emitted by this option for an exported symbol by including @dynamic in the comment documenting the symbol.

It is valid for .metadata.json files to contain errors. The template compiler reports these errors if the metadata is used to determine the contents of an annotation. The metadata collector cannot predict the symbols that are designed for use in an annotation. It preemptively includes error nodes in the metadata for the exported symbols. The template compiler can then use the error nodes to report an error if these symbols are used.

If the client of a library intends to use a symbol in an annotation, the template compiler does not normally report this. It gets reported after the client actually uses the symbol. This option allows detection of these errors during the build phase of the library and is used, for example, in producing Angular libraries themselves.

For library projects created with the Angular CLI, the development configuration default is true .

strictInjectionParameters link

When true , reports an error for a supplied parameter whose injection type cannot be determined. When false , constructor parameters of classes marked with @Injectable whose type cannot be resolved produce a warning. The recommended value is true , but the default value is false .

When you use the Angular CLI command ng new --strict , it is set to true in the created project's configuration.

strictTemplates link

When true , enables strict template type checking.

The strictness flags that this open enables allow you to turn on and off specific types of strict template type checking. See troubleshooting template errors.

When you use the Angular CLI command ng new --strict , it is set to true in the new project's configuration.

trace link

When true , prints extra information while compiling templates. Default is false .

Command line options link

Most of the time you interact with the Angular Compiler indirectly using Angular CLI. When debugging certain issues, you might find it useful to invoke the Angular Compiler directly. You can use the ngc command provided by the @angular/compiler-cli npm package to call the compiler from the command line.

The ngc command is just a wrapper around TypeScript's tsc compiler command and is primarily configured via the tsconfig.json configuration options documented in the previous sections.

Besides the configuration file, you can also use tsc command line options to configure ngc .