WordPress Same Slug Within Different Categories

WordPress plugin that allows duplicate post slugs when the permalink structure includes %category%.

Problem

WordPress enforces globally unique post_name values, even when the permalink structure (e.g., /%category%/%postname%/) makes URL collisions impossible. Two posts titled "Introduction" in different categories can't share the slug introduction — one gets introduction-2 despite their URLs being distinct (/category-a/introduction/ vs /category-b/introduction/).

This is WordPress core ticket #18962, open since 2011.

Solution

This plugin addresses three layers of the problem:

1. pre_wp_unique_post_slug — Skips the uniqueness suffix when %category% is in the permalink structure, allowing posts in different categories to share a slug.

2. posts_results — When WP_Query returns multiple posts with the same slug (because WordPress ignores category_name in the SQL for single post lookups), this filter narrows the results to the post belonging to the requested category.

3. redirect_canonical — Prevents WordPress from 301-redirecting a valid category-prefixed URL to a different post's URL.

Requirements

• WordPress 5.1+ (for pre_wp_unique_post_slug filter)
• Permalink structure must include %category% (e.g., /%category%/%postname%/)

The plugin is inert when the permalink structure doesn't include %category%.

Installation

1. Copy the wp-category-permalink-slugs directory to wp-content/plugins/
2. Activate via WP admin or wp plugin activate wp-category-permalink-slugs

After Activation

Existing posts with suffixed slugs (e.g., introduction-2) need to be manually corrected:

wp eval '
global $wpdb;
$wpdb->update($wpdb->posts, ["post_name" => "introduction"], ["ID" => <POST_ID>]);
clean_post_cache(<POST_ID>);
'
wp rewrite flush

The plugin only prevents future suffix additions. It does not retroactively fix existing slugs.

Limitations

• Only applies to the post post type. Pages and custom post types are unaffected.
• If any code uses get_page_by_path() without category context, it may return the wrong post when slugs collide. This is uncommon on content-focused sites.
• The posts_results filter only activates when the main query returns 2+ posts with the same slug — no performance impact on normal queries.

License

GPL-2.0-or-later