zulip/static/templates/settings/custom-user-profile-field.handlebars

<div class="user-name-section custom_user_field">
    <label for="{{ field_name }}" class="title">{{ field_name }}</label>
    {{#if is_long_text_field}}
    <textarea name="{{ field_name }}" id="{{ field_id }}">{{ field_value }}</textarea>
    {{else}}
    <input type="{{ field_type }}" name="{{ field_name }}" id="{{ field_id }}" value="{{ field_value }}" />
    {{/if}}
</div>