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Fixing Common All in One SEO Canonical URL Issues

31 threads Sep 10, 2025 Plugin → All in one seo

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Canonical URLs are a fundamental part of SEO, telling search engines which version of a page is the "master copy" to be indexed. The All in One SEO plugin handles this automatically, but users sometimes encounter problems where the generated canonical tag is incorrect, missing, or duplicated. This guide covers the most common canonical URL issues and how to resolve them.

Why Correct Canonical URLs Matter

An incorrect canonical URL can lead to SEO problems like duplicate content penalties, search engines indexing the wrong page version, or crawl errors. Common symptoms include seeing a double domain, a missing subfolder, or an entirely wrong URL in the <link rel="canonical"> tag.

Common Issues and Their Solutions

1. Incorrect Base Site URL

Problem: The most common cause of wrong canonical URLs is an incorrect WordPress Address (URL) or Site Address (URL). This can result in canonical links missing the 'www' prefix, not using HTTPS, or pointing to the wrong domain entirely.

Solution: The primary fix is to ensure your site's base URLs are correct in WordPress.

  1. Navigate to Settings > General in your WordPress dashboard.
  2. Check the WordPress Address (URL) and Site Address (URL) fields.
  3. If they are incorrect but greyed out, they are likely hardcoded in your wp-config.php file. You will need to define them there with lines like: 
    define('WP_HOME','https://www.yoursite.com');
define('WP_SITEURL','https://www.yoursite.com');
  4. After updating these URLs, resave your permalinks by going to Settings > Permalinks and clicking "Save Changes" without making any modifications.

2. Subfolder Installation Bug (Duplicate Path)

Problem: If WordPress is installed in a subfolder (e.g., yoursite.com/blog/), a known bug in older versions of All in One SEO could cause the subfolder to be duplicated in the canonical URL (e.g., yoursite.com/blog/blog/).

Solution: This issue was addressed in a plugin update. The first step is to ensure you are running the latest version of All in One SEO. If you are and the problem persists, you can use a filter to correct the URL manually until the update is applied.

3. Removing or Modifying the Canonical URL with Code

Problem: You may need to remove the canonical tag on specific pages, like search results pages, or modify it to fit a custom structure.

Solution: All in One SEO provides the aioseo_canonical_url filter hook for this purpose. You can add code to your child theme's functions.php file or a code snippets plugin.

To remove the canonical tag on search pages:

add_filter( 'aioseo_canonical_url', function( $canonicalUrl ) {
 if ( is_search() ) {
  return '';
 }
 return $canonicalUrl;
} );

To completely remove the canonical tag from a page if a value is set:

add_filter( 'aioseo_canonical_url', 'remove_canonical_url', 10, 1 );
function remove_canonical_url( $url ) {
 return '';
}

To modify a paginated comment page canonical URL:

add_filter( 'aioseo_canonical_url', 'custom_aioseo_canonical_url', 10, 1 );
function custom_aioseo_canonical_url( $url ) {
 return preg_replace( '%/comment-page-d+/(#comments)?$%', '/', $url );
}

4. Manual Canonical URL Setting

For individual posts or pages, you can override the automatically generated canonical URL directly within the All in One SEO meta box.

  1. Edit the post or page in WordPress.
  2. Scroll down to the All in One SEO settings panel.
  3. Click on the Advanced tab.
  4. Enter the correct URL in the Canonical URL field.

Troubleshooting Steps

  • Clear Caches: After making any changes, clear your WordPress cache (if using a caching plugin) and your browser cache before checking the source code again.
  • Conflict Test: If issues persist, perform a conflict test. Use the Health Check & Troubleshooting plugin to temporarily disable all other plugins and switch to a default theme (like Twenty Twenty-Four) to see if the problem is resolved. If it is, reactivate your plugins and theme one by one to identify the culprit.
  • Check Google Search Console: Use the URL Inspection Tool to submit corrected URLs to Google for re-crawling after fixes are implemented.

By following these steps, you can diagnose and fix the majority of canonical URL issues, ensuring your site sends the correct signals to search engines.

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