govuk-frontend/dist/govuk/components/character-count/template-default.html

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

<div class="govuk-form-group govuk-character-count" data-module="govuk-character-count" data-maxlength="10">
  <label class="govuk-label" for="more-detail">
    Can you provide more detail?
  </label>
  <textarea class="govuk-textarea govuk-js-character-count" id="more-detail" name="more-detail" rows="5" aria-describedby="more-detail-info"></textarea>
  <div id="more-detail-info" class="govuk-hint govuk-character-count__message">
    You can enter up to 10 characters
  </div>
</div>