govuk-frontend/dist/govuk/components/file-upload/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">
  <label class="govuk-label" for="file-upload-1">
    Upload a file
  </label>
  <input class="govuk-file-upload" id="file-upload-1" name="file-upload-1" type="file">
</div>