Background

Each time we upload a file to the Media Library, WordPress stores the file in the uploads folder and creates a new attachment. Attachments are instances of the 'attachment' built-in post type.

Attachment pages are useful to display information about the underlying file, as I do here, but website owners may prefer to bypass these intermediate pages and link directly to the file.

Theory

The fact that a new attachment is created each time we upload a file to the Media Library cannot be disabled, but we can make these pages unreachable.

In the next section, I propose a solution that uses the 'template_redirect' action to redirect attachment pages to the underlying file. I also use the 'attachment_link' filter to replace the attachment page URL with the file URL to avoid unnecessary redirects.

Steps

Follow these steps to bypass attachment pages in WordPress.

Step 1: Add the following code to WordPress.

/*
 * Performs a redirect from an attachment page to the underlying file.
 */
function ns_redirect_attachment(){

    if(is_attachment()){
        $attachment_ID = get_queried_object_id();
        $file_url = wp_get_attachment_url($attachment_ID);
        wp_redirect($file_url, 301);
        exit();
    }
}
add_action('template_redirect', 'ns_redirect_attachment', 10, 0);

/*
 * Replaces the attachment page URL with the URL of the underlying file.
 */
function ns_replace_attachment_link($link, $post_ID){
    return wp_get_attachment_url($post_ID) ?: $link;
}
add_filter('attachment_link', 'ns_replace_attachment_link', 10, 2);

Step 2: Try to visit an attachment page and verify that the underlying file is opened.

Exercise

Develop a solution that redirects each attachment to the post it is attached to. If the attachment is not attached to a post, redirect to the underlying file. Customize the attachment link accordingly.

Source code

The source code developed in this tutorial, including a possible answer to the exercise, is available here.