Quickly output a 404 for static files that aren’t found, rather than loading the normal 404 page.
Any static files ( images, text, pdfs, etc ) that don’t exist will 404 as soon as possible, rather than loading the entire WordPress application.
By default, the list of extensions to check are the results of wp_get_ext_types, but can be filtered with static_404_extensions.
The output is a static page with the text 404 Not Found, this text can be edited by filtering static_404_message.
A 404 status code will be used, but can be filtered with static_404_response_code.
Passing true to static_404_should_process_request will short-circuit and skip processing the request. This filter gets passed the current request.