create a clean wordpress header and remove unnecessary clutter.

wpa-clean-header.php

<?php
/*
Plugin Name: wordpress assist clean header
Plugin URI: http://www.wordpressassist.nl/
Description: Remove shortlink hook
Version: 1.0
Author: AukeJomm
Author URI: http://www.aukejongbloed.nl
*/
      
remove_action('wp_head', 'rsd_link'); // remove really simple discovery link
remove_action('wp_head', 'wp_generator'); // remove wordpress version

remove_action('wp_head', 'feed_links', 2); // remove rss feed links (make sure you add them in yourself if youre using feedblitz or an rss service)
remove_action('wp_head', 'feed_links_extra', 3); // removes all extra rss feed links

remove_action('wp_head', 'index_rel_link'); // remove link to index page
remove_action('wp_head', 'wlwmanifest_link'); // remove wlwmanifest.xml (needed to support windows live writer)

remove_action('wp_head', 'start_post_rel_link', 10, 0); // remove random post link
remove_action('wp_head', 'parent_post_rel_link', 10, 0); // remove parent post link
remove_action('wp_head', 'adjacent_posts_rel_link', 10, 0); // remove the next and previous post links
remove_action('wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0 );
      
remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
remove_action( 'wp_print_styles', 'print_emoji_styles' );
      
remove_action('wp_head', 'wp_shortlink_wp_head', 10, 0); // Remove shortlink

/*
* Remove JSON API links in header html
*/
function remove_json_api () {

    // Remove the REST API lines from the HTML Header
    remove_action( 'wp_head', 'rest_output_link_wp_head', 10 );
    remove_action( 'wp_head', 'wp_oembed_add_discovery_links', 10 );

    // Remove the REST API endpoint.
    remove_action( 'rest_api_init', 'wp_oembed_register_route' );

    // Turn off oEmbed auto discovery.
    add_filter( 'embed_oembed_discover', '__return_false' );

    // Don't filter oEmbed results.
    remove_filter( 'oembed_dataparse', 'wp_filter_oembed_result', 10 );

    // Remove oEmbed discovery links.
    remove_action( 'wp_head', 'wp_oembed_add_discovery_links' );

    // Remove oEmbed-specific JavaScript from the front-end and back-end.
    remove_action( 'wp_head', 'wp_oembed_add_host_js' );

   // Remove all embeds rewrite rules.
   add_filter( 'rewrite_rules_array', 'disable_embeds_rewrites' );

}
add_action( 'after_setup_theme', 'remove_json_api' );

/*
	Snippet completely disable the REST API and shows {"code":"rest_disabled","message":"The REST API is disabled on this site."} 
	when visiting http://yoursite.com/wp-json/
*/
function disable_json_api () {

  // Filters for WP-API version 1.x
  add_filter('json_enabled', '__return_false');
  add_filter('json_jsonp_enabled', '__return_false');

  // Filters for WP-API version 2.x
  add_filter('rest_enabled', '__return_false');
  add_filter('rest_jsonp_enabled', '__return_false');

}
add_action( 'after_setup_theme', 'disable_json_api' );

Thanks Auke! One of the best lists I've seen.

We were inspired to make a free plugin recently, would appreciate any feedback:

https://wordpress.org/plugins/header-cleanup-littlebizzy/

[error] 24281#24281: *501 FastCGI sent in stderr: "PHP message: PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'disable_embeds_rewrites' not found or invalid function name in /usr/share/nginx/html/bbb/wp-includes/class-wp-hook.php on line 286" whilereading response header from upstream

[error] 24281#24281: *501 FastCGI sent in stderr: "PHP message: PHP Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'disable_embeds_rewrites' not found or invalid function name in /usr/share/nginx/html/bbb/wp-includes/class-wp-hook.php on line 286" whilereading response header from upstream

It appears that you're adding a filter here, but there is no matching function named "disable_embeds_rewrites" being declared.

A quick Google search returns a Kinsta article that uses this same filter and has some more complete code.

function disable_embeds_rewrites($rules) {
    foreach($rules as $rule => $rewrite) {
        if(false !== strpos($rewrite, 'embed=true')) {
            unset($rules[$rule]);
        }
    }
    return $rules;
}

Some parameters can be redundant like in remove_action( 'wp_head', 'rest_output_link_wp_head', 10 ); third param "priority" has 10 as default value, so you don't have to write it again.

wlwmanifest_link is deprecated in 6.3.0 and no longer included in core so it might be redundant to add.