govuk-frontend/dist/govuk/components/accordion/template-with-one-section-open.html

GOV.UK Frontend contains the code you need to start building a user interface for government platforms and services.

<div class="govuk-accordion" data-module="govuk-accordion" id="one-section-open-example">
  <div class="govuk-accordion__section govuk-accordion__section--expanded">
    <div class="govuk-accordion__section-header">
      <h2 class="govuk-accordion__section-heading">
        <span class="govuk-accordion__section-button" id="one-section-open-example-heading-1">
          Section A
        </span>
      </h2>
    </div>
    <div id="one-section-open-example-content-1" class="govuk-accordion__section-content">
      <ul class="govuk-list govuk-list--bullet">
        <li>Example item 1</li>
      </ul>
    </div>
  </div>
  <div class="govuk-accordion__section">
    <div class="govuk-accordion__section-header">
      <h2 class="govuk-accordion__section-heading">
        <span class="govuk-accordion__section-button" id="one-section-open-example-heading-2">
          Section B
        </span>
      </h2>
    </div>
    <div id="one-section-open-example-content-2" class="govuk-accordion__section-content">
      <ul class="govuk-list govuk-list--bullet">
        <li>Example item 2</li>
      </ul>
    </div>
  </div>
</div>