How to disable and remove old post revisions in WordPress (including multisite)

If you don’t want to use a plugin to clean up your WordPress website and insist on custom coding it, here is how to remove post revisions in a single website or a multisite network.

Add the code below to your theme or plugin, and trigger it using an action or a form or an event.

Disclaimer: Do not run it immediately, and do not activate it in production.

/**
 * Delete all revisions from all posts in a single WordPress installation or a network.
 */

// Give the script 5 minutes to run.
set_time_limit( 60 * 5 );

/**
 * Get a list of all blogs in our network.
 */
$blog_list = get_blog_list_full( 0, 'all' );

// Delete revisions for each blog.
foreach ( $blog_list as $blog ) {
    echo '<p>Deleting from ' . $blog['domain'] . ':</p>';
    echo delete_revisions_for_blog( $blog['blog_id'] ) . ' revisions.';
    flush();
}

echo '<p>Done.<p>';

/**
 * Delete all revisions for posts in a blog.
 *
 * @param int $blog_id The ID of the blog to delete revisions from.
 *
 * @return int The number of revisions deleted.
 */
function delete_revisions_for_blog( $blog_id ) {
    global $wpdb;

    if ( is_multisite() ) {
        switch_to_blog( $blog_id );
    }

    // Retrieve revision IDs that are not autosave revisions.
    $revision_ids = $wpdb->get_col( "SELECT ID FROM $wpdb->posts WHERE post_type = 'revision' AND post_name NOT LIKE '%-autosave%'" );

    // Delete each revision, including related meta and taxonomy terms.
    foreach ( $revision_ids as $revision_id ) {
        wp_delete_post_revision( (int) $revision_id );
    }



    if ( is_multisite() ) {
        restore_current_blog();
    }

    // Return the number of revisions deleted.
    return count( $revision_ids );
}

/**
 * Get a list of blogs in a multisite network.
 *
 * @param int    $start      Offset for the list.
 * @param string $num        Number of blogs to retrieve. Use 'all' to get all blogs.
 * @param string $deprecated Deprecated parameter (not used).
 *
 * @return array An array of blog details (blog_id and domain).
 */
function get_blog_list_full( $start = 0, $num = 10, $deprecated = '' ) {
    global $wpdb, $blog_id;

    // For single blogs
    if ( ! is_multisite() ) {
        return [
            $blog_id => [
                'blog_id' => $blog_id,
                'domain'  => preg_replace( '%https?://%i', '', get_bloginfo( 'url', 'raw' ) ),
            ]
        ];
    }

    // For multisite setups
    $blogs = $wpdb->get_results( $wpdb->prepare( "SELECT blog_id, domain FROM $wpdb->blogs WHERE site_id = %d AND deleted = '0' ORDER BY registered ASC", $wpdb->siteid ), ARRAY_A );

    $blog_list = [];

    // Build an array of blog details.
    foreach ( (array) $blogs as $details ) {
        $blog_list[ $details['blog_id'] ] = $details;
    }

    // Ensure $blog_list is an array.
    if ( ! is_array( $blog_list ) ) {
        return [];
    }

    // Return blogs based on the specified number.
    if ( (string) $num === 'all' ) {
        return array_slice( $blog_list, $start );
    } else {
        return array_slice( $blog_list, $start, (int) $num );
    }
}

To disable revisions in WordPress, you can define the WP_POST_REVISIONS constant in your wp-config.php file. To completely disable post revisions, you can set it to false or 0. Here’s how to do it:

Open your wp-config.php file for editing. You can find it in the root directory of your WordPress installation.
Add the following line to your wp-config.php file, preferably just above the line that says /* That's all, stop editing! Happy publishing. */: