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);
  });
});

APIs

AccordionGroup

The container directive that manages keyboard navigation and expansion behavior for a group of accordion items.

Inputs

Property Type Default Description
disabled boolean false Disables all triggers in the group
multiExpandable boolean true Whether multiple panels can be expanded simultaneously
softDisabled boolean true When true, disabled items are focusable. When false, they are skipped
wrap boolean false Whether keyboard navigation wraps from last to first item and vice versa

Methods

Method Parameters Description
expandAll none Expands all panels (only works when multiExpandable is true)
collapseAll none Collapses all panels

AccordionTrigger

The directive applied to the button element that toggles panel visibility.

Inputs

Property Type Default Description
panel AccordionPanel — Required. The reference of the controlled accordion panel.
id string auto Unique identifier for the trigger
disabled boolean false Disables this trigger
expanded boolean false Whether the panel is expanded (supports two-way binding)

Signals

Property Type Description
active Signal<boolean> Whether the trigger currently has focus

Methods

Method Parameters Description
expand none Expands the associated panel
collapse none Collapses the associated panel
toggle none Toggles the panel expansion state

AccordionPanel

The directive applied to the element containing the collapsible content.

Inputs

Property Type Default Description
id string auto Unique identifier for the panel
preserveContent boolean true Whether to keep content in DOM after panel collapses

Signals

Property Type Description
visible Signal<boolean> Whether the panel is currently expanded

Methods

Method Parameters Description
expand none Expands this panel
collapse none Collapses this panel
toggle none Toggles the expansion state

AccordionContent

The structural directive applied to an ng-template inside an accordion panel to enable lazy rendering.

This directive has no inputs, outputs, or methods. Apply it to an ng-template element:

<div ngAccordionPanel #panel1="ngAccordionPanel">
  <ng-template ngAccordionContent>
    <!-- Content here is lazily rendered -->
  </ng-template>
</div>