Alternate content links

_hrefLang.twig

{# Include in the head of the base page template #}

{% set currentElement = craft.app.urlManager.matchedElement %}
{% set sites = craft.app.getSites().getGroupById(currentSite.groupId).getSites()|filter(s => s.baseUrl is not empty) %}
{% set altLinks = [] %}

{% for site in sites %}

    {% set title = craft.app.i18n.getLocaleById(site.language).displayName %}
    {% set url = site.getBaseUrl() %}
    {% if currentElement %}
        {% set otherLocaleElement = craft.app.getElements().getElementById(currentElement.id, currentElement.className(), site.id) %}
        {% if otherLocaleElement and otherLocaleElement.enabledForSite %}
            {% set url = otherLocaleElement.url %}
        {% endif %}
    {% endif %}

    {% set altLinks = altLinks|merge([{
        url: url,
        title: title,
        countryCode: site.language|split('-')|last,
        current: site.id == currentSite.id ? true : false,
        language: site.language,
    }]) %}

{% endfor %}

{% if altLinks|length > 1 %}
    {% for altLink in altLinks %}
        <link rel="alternate" href="{{ altLink.url }}" hreflang="{{ altLink.language }}" />
    {% endfor %}
{% endif %}