In-depth Guides
Angular Aria

Accordion

Overview

An accordion organizes related content into expandable and collapsible sections, reducing page scrolling and helping users focus on relevant information. Each section has a trigger button and a content panel. Clicking a trigger toggles the visibility of its associated panel.

Usage

Accordions work well for organizing content into logical groups where users typically need to view one section at a time.

Use accordions when:

  • Displaying FAQs with multiple questions and answers
  • Organizing long forms into manageable sections
  • Reducing scrolling on content-heavy pages
  • Progressively disclosing related information

Avoid accordions when:

  • Building navigation menus (use the Menu component instead)
  • Creating tabbed interfaces (use the Tabs component instead)
  • Showing a single collapsible section (use a disclosure pattern instead)
  • Users need to see multiple sections simultaneously (consider a different layout)

Features

  • Expansion modes - Control whether one or multiple panels can be open at the same time
  • Keyboard navigation - Navigate between triggers using arrow keys, Home, and End
  • Lazy rendering - Content is only created when a panel first expands, improving initial load performance
  • Disabled states - Disable the entire group or individual triggers
  • Focus management - Control whether disabled items can receive keyboard focus
  • Programmatic control - Expand, collapse, or toggle panels from your component code
  • RTL support - Automatic support for right-to-left languages

Examples

Single expansion mode

Set [multiExpandable]="false" to allow only one panel to be open at a time. Opening a new panel automatically closes any previously open panel.

This mode works well for FAQs or situations where you want users to focus on one answer at a time.

Multiple expansion mode

Set [multiExpandable]="true" to allow multiple panels to be open simultaneously. Users can expand as many panels as needed without closing others.

This mode is useful for form sections or when users need to compare content across multiple panels.

NOTE: The multiExpandable input defaults to true. Set it to false explicitly if you want single expansion behavior.

Disabled accordion items

Disable specific triggers using the disabled input. Control how disabled items behave during keyboard navigation using the softDisabled input on the accordion group.

When [softDisabled]="true" (the default), disabled items can receive focus but cannot be activated. When [softDisabled]="false", disabled items are skipped entirely during keyboard navigation.

Lazy content rendering

Use the ngAccordionContent directive on an ng-template to defer rendering content until the panel first expands. This improves performance for accordions with heavy content like images, charts, or complex components.

<div ngAccordionGroup>
  <div>
    <button ngAccordionTrigger [panel]="panel1">Trigger Text</button>
    <div ngAccordionPanel #panel1="ngAccordionPanel">
      <ng-template ngAccordionContent>
        <!-- This content only renders when the panel first opens -->
        <img src="large-image.jpg" alt="Description" />
        <app-expensive-component />
      </ng-template>
    </div>
  </div>
</div>

By default, content remains in the DOM after the panel collapses. Set [preserveContent]="false" to remove the content from the DOM when the panel closes.

Testing

Angular Aria provides component harnesses for testing accordion components. Here is an example of how to use the harnesses in a component test:

import {ComponentFixture, TestBed} from '@angular/core/testing';
import {HarnessLoader} from '@angular/cdk/testing';
import {TestbedHarnessEnvironment} from '@angular/cdk/testing/testbed';
import {AccordionGroupHarness} from '@angular/aria/accordion/testing';
import {MyAccordionComponent} from './my-accordion'; // Your component

describe('MyAccordionComponent', () => {
  let fixture: ComponentFixture<MyAccordionComponent>;
  let loader: HarnessLoader;

  beforeEach(async () => {
    TestBed.configureTestingModule({
      imports: [MyAccordionComponent],
    });

    fixture = TestBed.createComponent(MyAccordionComponent);
    await fixture.whenStable();
    loader = TestbedHarnessEnvironment.loader(fixture);
  });

  it('should allow expanding panels', async () => {
    // Load the accordion group harness
    const group = await loader.getHarness(AccordionGroupHarness);

    // Get all individual accordions (items) in the group
    const accordions = await group.getAccordions();
    expect(accordions.length).toBe(3);

    // Verify initial state (first expanded, others collapsed)
    expect(await accordions[0].isExpanded()).toBe(true);
    expect(await accordions[1].isExpanded()).toBe(false);

    // Expand the second panel
    await accordions[1].expand();

    // Verify updated state
    expect(await accordions[1].isExpanded()).toBe(true);
    // If multiExpandable is false, the first one should now be collapsed
    expect(await accordions[0].isExpanded()).toBe(false);
  });
});

API reference

For detailed API documentation, inspect the following API references: