Global multilingual sitemap for Jekyll based websites

sitemap.xml

---
# Global multilingual sitemap for Jekyll based websites
#
# Version: 1.0.0
# Author: Vivien Richter <vivien-richter@outlook.de>
# License: CC-BY-4.0
#
# Based on: https://sylvaindurand.org/making-jekyll-multilingual/#with-a-sitemaps-file
#
# See also:
# - https://developers.google.com/search/docs/advanced/crawling/localized-versions
# - https://www.sitemaps.org/de/protocol.html

layout: null
---
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
  xmlns:xhtml="http://www.w3.org/1999/xhtml"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
  <!-- Posts -->
  {%- for post in site.posts -%}
  {%- unless post.published == false or post.sitemap == false %}
  <url>
    <loc>{{ site.url }}{{ post.url }}</loc>
    {%- assign translations = site.posts | where:"ref", post.ref -%}
    {%- for translation in translations %}
    <xhtml:link
               rel="alternate"
               hreflang="{{ translation.locale }}"
               href="{{ site.url }}{{ translation.url }}"/>
    {%- endfor %}
    <xhtml:link
               rel="alternate"
               hreflang="x-default"
               href="{{ site.url }}"/>
    <lastmod>{{ post.date | date_to_xmlschema }}</lastmod>
    <changefreq>{{ post.changefreq }}</changefreq>
    <priority>{{ post.priority }}</priority>
  </url>
  {%- endunless -%}
  {%- endfor %}
  <!-- Pages -->
  {%- assign pages = site.pages | where: "sitemap", true -%}
  {%- for page in pages %}
  <url>
    <loc>{{ site.url }}{{ page.url }}</loc>
    {%- assign translations = pages | where:"ref", page.ref -%}
    {%- for translation in translations %}
    <xhtml:link
               rel="alternate"
               hreflang="{{ translation.locale }}"
               href="{{ site.url }}{{ translation.url }}"/>
    {%- endfor %}
    <xhtml:link
               rel="alternate"
               hreflang="x-default"
               href="{{ site.url }}"/>
    <lastmod>{{ page.last_modified_at | date_to_xmlschema }}</lastmod>
    <changefreq>{{ page.changefreq }}</changefreq>
  </url>
  {%- endfor %}
</urlset>

Required front matter YAML:

Example for pages:

ref : about # Please use the same reference for different translations of the same post
locale : en-us
sitemap : true # Visibility in the global sitemap
priority : 0.5 # Between 0.0 and 1.0
changefreq : "yearly" # Possible values: always, hourly, daily, weekly, monthly, yearly, never

Example for posts:

ref : about # Please use the same reference for different translations of the same page
locale : en-us
sitemap : true # Visibility in the global sitemap

Required Jekyll plugins:

• jekyll-last-modified-at