Samuel Aguilera

There are three possible scenarios where this plugin does something. In all cases, the attachment page must exists, the plugin will not run for deleted attachments:
A) A visitor lands on an attachment page and the parent post is available (not in trash or deleted). A 301 redirect will be issued to redirect the visitor to the parent post.
B) A visitor lands on an attachment page and the parent post was already deleted from trash. A 302 redirect is issued to home page (this can be changed to 301 if you want, see FAQ for more details).
C) A visitor lands on an attachment page and the parent post is in trash, therefore not available for the visitor. It returns a 404 error code to prevent endless redirection loop in old WP releases and redirecting to trashed/not available posts.
There is no options page, simply activate it and will do the job.
If you’re happy with the plugin <a href="https://wordpress.org/support/plugin/attachment-pages-redirect/reviews/?filter=5" rel="ugc">please don’t forget to give it a good rating</a>, it will motivate me to keep sharing and improving this plugin (and others).
<h4>Requirements</h4>
<ul>
<li>WordPress 4.8 or higher.</li>
</ul>

Attachment Pages Redirect

Redirect attachment pages or return a 404 error for them based on the parent post status.

Redirects visitors to the the site’s URL as it appears in the WordPress database in case they’re not already connecting through that domain. This is handy for secondary domains that point to your WordPress site.
For example, if example.com and example.net both point to your server, WordPress will normally serve the same site regardless of what the user types in their address bar. 
With this plugin enabled, users visiting the secondary domain will be automatically redirected to whichever domain is configured as the “Site Address (URL)” under WordPress’ “General Settings” page.

Multidomain Redirect

Redirects visitors to the the site's URL as it appears in the WordPress database in case they're not already connecting through that domain.

Attachment Pages Redirect vs Multidomain Redirect