Solving The 404 Error For Custom Post Types In Wordpress

Troubleshooting 404 Errors for Custom Post Types

A 404 error, meaning a “404 Page Not Found” error, occurs when a user attempts to access a page or resource that does not exist on a website. With custom post types (CPTs) in WordPress, it is possible for invalid URLs for custom content to trigger frustrating 404 errors.

CPTs allow developers to create customized content structures in WordPress beyond the default posts and pages. However, CPT permalinks can easily become invalid and return 404s if not properly configured. Troubleshooting these errors requires verifying CPT registration settings, testing permalinks, and debugging .htaccess configs.

Registering Custom Post Types

Properly registering a custom post type is the first step toward avoiding invalid CPT URLs. Here is example code for registering the custom post type “book”:

Table of Contents

function create_book_cpt() {

  $labels = array( 
    'name' => 'Books',
    'singular_name' => 'Book'
  );

  $args = array(
    'labels'             => $labels,
    'public'             => true,
    'has_archive'        => true,
    'supports'           => array( 'title', 'editor', 'excerpt', 'thumbnail' ),
    'taxonomies'		 => array( 'genres' ),    
    'rewrite' 		 => array( 'slug' => 'books' ),
    'show_in_rest'       => true
  );

  register_post_type( 'book', $args );
}

add_action( 'init', 'create_book_cpt' );

Pay particular attention to the rewrite argument which controls the permalink slug, as well as public which allows it to be publicly queried. Improper rewrite settings are a common culprit behind invalid CPT URLs.

Setting Up Permalinks

The permalink settings must match the rewrite rules for custom post types to avoid 404s. To enable “post name” permalinks for the “book” custom post type, you would select the Post name option under Settings > Permalinks.

This allows URLs like /books/sample-book/ to be valid. The path must match the registered rewrite slug we specified when registering “book” custom post type.

Debugging 404 Errors

To debug 404 errors for custom post types:

Check that the CPT is properly registered in functions.php
Confirm that permalink settings match the registered rewrite rules
Test actual post permalinks like /books/my-book to see if valid
Look for rewrite rules related to custom post types in the .htaccess file

Pay attention for clues in error logs indicating conflicts, bad requests for invalid CPT URLs, or rewrite rules not being generated properly.

Additional Troubleshooting Tips

Some additional things to check regarding custom post type 404 errors:

Plugin conflicts – Disable other plugins to test for conflicts
Debug plugins – Use a CPT inspection tool for more diagnostics
Permalink reset – Sometimes resetting the permalinks can clear out invalid rules

Doing a full WordPress reinstallation can also help eliminate conflicts that may be blocking proper CPT rewrite functionality.

Example Custom Post Type Code

Here is an example showing complete registration code for a complex “book” custom post type with multiple taxonomies and endpoints.

function create_book_cpt() {

  $labels = array(
    // Labels for the post type
  );  

  $args = array(
      
    'labels' => $labels,
    'public' => true,
    'rewrite' => array( 'slug' => 'books' ),
    'has_archive' => true,
    'taxonomies'		 => array( 'genres', 'publishers' ),
    'menu_icon'   => 'dashicons-book',
    'supports'           => array( 'title', 'editor', 'excerpt', 'thumbnail', 'revisions' ),
    'show_in_rest'       => true,
    
    // Registering custom taxonomies

    'capability_type'    => 'post',
    'map_meta_cap' => true,
  );
    

  register_post_type( 'book', $args ); 

} 

add_action( 'init', 'create_book_cpt' );


function create_book_taxonomies() {

  // Register custom taxonomies
}

add_action( 'init', 'create_book_taxonomies', 0 );

Focus on args related to rewrites, permalinks, and rest API support when troubleshooting 404 errors.

Redirecting 404s for a Smooth UX

Redirecting failed CPT URLs is crucial to send users to a relevant page rather than a “Page Not Found” dead end.

function cpt_404_redirect() {

  if ( is_404() ) {

    $url = get_permalink( get_option( 'page_for_posts' ) );  
    wp_redirect( $url, 301 );
    exit;

  }

}

add_action( 'template_redirect', 'cpt_404_redirect' );

This example would forward users hitting invalid CPT URLs to the homepage. You may also consider custom redirect rules based on post type.

Summary and Final Recommendations

In summary, properly registering and configuring rewrite rules, permalinks, and .htaccess for custom post types is crucial to avoiding pesky 404 errors.

Use descriptive slugs, test actual post URLs
Ensure CPTs are set to public
Mind plugin conflicts, debug issues early
Redirect failed URLs for a better user experience

Additional resources:

Solving The 404 Error For Custom Post Types In WordPress