<link rel=“canonical” href=“/relative/url” />

Question

Drupal 8 creates <link rel="canonical" href="/relative/url" /> by default. support.google.com says:

Use absolute paths rather than relative paths with the rel="canonical" link element.

Use this structure: https://www.example.com/dresses/green/greendresss.html Not this structure: /dresses/green/greendress.html

I used the Google Search Console URL Inspection and found Google does not recognize relative urls as canonical. It says:

User-declared canonical N/A

I believe this is causing some indexing problems for our multiple language website. How can we convert the canonical urls to absolute as recommended by Google?

Answer 1

The following function updates the rel tags in the head section of all pages on a website. The "revision" and "shortlink" tags are deleted using unset(). The "canonical" tag is converted from a relative to an absolute url. This function should be called from modulename_preprocess_html() of your custom module.

function canonical_shortlink_revision(&$variables) {

  foreach($variables['page']['content']['system_main']['#attached']['html_head_link'] as $key => $value) {

    if( ($value[0]["rel"] === "revision") || ($value[0]["rel"] === "shortlink") )
      unset($variables['page']['content']['system_main']['#attached']['html_head_link'][$key]);

    if($value[0]["rel"] === "canonical") {
      $href = $variables['page']['content']['system_main']['#attached']['html_head_link'][$key][0]["href"];
      $href = \Drupal::request()->getSchemeAndHttpHost() . $href;
      $variables['page']['content']['system_main']['#attached']['html_head_link'][$key][0]["href"] = $href;
    }

  }
}

Answer 2

The metatag module gives you the ability to overwrite the 'canonical' metatag:

• On the module's settings page (/admin/config/search/metatag)
• Edit the General type
• Under Advanced you'll find the Canonical field
• Set the field's value to [current-page:url:absolute]
• Save

That should do it. The instructions above are for Drupal 8.

Update 1:

If you are comfortable using hooks and working with PHP you may also use a theme hook (hook_page_attachments_alter) to achieve the same thing. Here's the api spec on drupal.org for the function.