This snippet contains a set of rules for disabling various unnecessary WordPress features to clean up the HTML view as much as possible and speed up page loading

MCleaner

<?php

/**
 * This snippet contains a set of rules for disabling various unnecessary WordPress features to clean up the HTML view as much as possible and speed up page loading.
 *
 * !This is an experimental version and some rules may affect the functionality of your site, so uncomment the rules that are not needed for your project.
 * 
 * @package mcleaner
 */

/** ==================================
 * Disable the Gutenberg block editor.
 * ===================================
 */
add_filter('use_block_editor_for_post_type', '__return_false', 10);

/**
 * Remove the Gutenberg block library CSS from loading on the frontend.
 */
function remove_wp_block_library_css()
{
    wp_dequeue_style('wp-block-library');
    wp_dequeue_style('wp-block-library-theme');
    wp_dequeue_style('wc-blocks-style'); // Remove WooCommerce block CSS
    wp_deregister_style('wp-block-library');
}
add_action('wp_enqueue_scripts', 'remove_wp_block_library_css', 100);

/** ==================================
 * W3C Validate
 * ===================================
 */
/**
 * Remove trailing slash from meta
 *
 * This function uses output buffering to replace trailing slash from the output
 * of wp_head action. It removes the closing slash from meta tags to make the
 * HTML code valid.
 *
 * @return void
 */
function w3c_fix_trailing_slash()
{
    ob_start(function ($output) {
        return preg_replace('/\s*\/>/', '>', $output);
    });
}
add_action('wp', 'w3c_fix_trailing_slash');

/**
 * Remove unnecessary attributes from HTML code to fix validation errors
 */
function w3c_fix_types_error()
{
    // Start output buffering and apply callback function to strip attributes
    ob_start(function ($fix_w3c_type) {
        $fix_w3c_type = str_replace(array('type="text/javascript"', 'type="application/javascript"', "type='text/javascript'"), '', $fix_w3c_type);
        $fix_w3c_type = str_replace(array('type="text/css"', "type='text/css'"), '', $fix_w3c_type);
        $fix_w3c_type = str_replace(array('frameborder="0"', "frameborder='0'"), '', $fix_w3c_type);
        $fix_w3c_type = str_replace(array('scrolling="no"', "scrolling='no'"), '', $fix_w3c_type);
        return $fix_w3c_type;
    });
}
add_action('template_redirect', 'w3c_fix_types_error');

/** ==================================
 * Removing unnecessary code
 * ===================================
 */
// Remove the inline styles created by add_theme_support('custom-background')
add_action('wp_head', 'remove_custom_background_style');
function remove_custom_background_style()
{
    ob_start(function ($output) {
        $pattern = '/<style\s+id="custom-background-css"[^>]*>.*?<\/style>/is';
        return preg_replace($pattern, '', $output);
    });
}

/**
 * Remove links
 */
remove_action('wp_head', 'rsd_link'); // Removes the RSD link for a deleted publication
remove_action('wp_head', 'wlwmanifest_link'); // Removes the Windows link for the Live Writer
remove_action('wp_head', 'wp_shortlink_wp_head', 10, 0); // Removes the short link
remove_action('template_redirect', 'wp_shortlink_header', 11, 0); // Removes the short link header
remove_action('wp_head', 'wp_generator'); // Removes information about the version of WordPress
remove_action('wp_head', 'adjacent_posts_rel_link', 10, 0); // Removes links to the previous and next articles
remove_action('wp_head', 'adjacent_posts_rel_link_wp_head', 10, 0); // Removes links to the previous and next articles
remove_action('wp_head', 'index_rel_link'); // Removes the index link
remove_action('wp_head', 'start_post_rel_link', 10, 0); // Removes the start link
remove_action('wp_head', 'parent_post_rel_link', 10, 0); // Removes the parent link

/** ===================================================
 *  SET disables
 * ====================================================
 */
/**
 * Remove the "ver" parameter from scripts and styles.
 *
 * @param string $src The script or style URL.
 * @return string The URL without the "ver" parameter.
 */
function remove_wp_ver_css_js($src)
{
    if (strpos($src, 'ver=')) {
        $src = remove_query_arg('ver', $src);
    }
    return $src;
}
add_filter('style_loader_src', 'remove_wp_ver_css_js', 9999);
add_filter('script_loader_src', 'remove_wp_ver_css_js', 9999);

// Deregister the 'classic-theme-styles' script with priority 20
add_action('wp_enqueue_scripts', 'mcleaner_child_deregister_styles', 20);
function mcleaner_child_deregister_styles()
{
    wp_dequeue_style('classic-theme-styles');
}

// Remove the 'wp_enqueue_global_styles' and 'wp_global_styles_render_svg_filters' actions on 'init' action
function mcleaner_remove_global_css()
{
    remove_action('wp_enqueue_scripts', 'wp_enqueue_global_styles');
    remove_action('wp_body_open', 'wp_global_styles_render_svg_filters');
}
add_action('init', 'mcleaner_remove_global_css');

/**
 * Remove the DNS prefetch.
 */
remove_action('wp_head', 'wp_resource_hints', 2);

/**
 * Disables pings.
 */
function mcleaner_remove_x_pingback($headers)
{
    unset($headers['X-Pingback']);
    return $headers;
}

/**
 * Disables comment styles.
 */
function mcleaner_remove_recent_comments_style()
{
    global $wp_widget_factory;
    remove_action('wp_head', array($wp_widget_factory->widgets['WP_Widget_Recent_Comments'], 'recent_comments_style'));
}

/** =============================================
 * Disables the RSS feed.
 * ==============================================
 */
/**
 * Removes RSS feed links of the entry and comments,
 * removes category and archive RSS feed links,
 * disables the RSS feed,
 * removes the DNS prefetch,
 * disables pings and comment styles.
 */

// Removes RSS feed links of the entry and comments
remove_action('wp_head', 'feed_links', 2);

// Removes category and archive RSS feed links
remove_action('wp_head', 'feed_links_extra', 3);

/**
 * Disables various links in the WordPress head section
 */
function fb_disable_feed()
{
    wp_redirect(get_option('siteurl'));
}
// Disable RSS feed
add_action('do_feed', 'fb_disable_feed', 1);
add_action('do_feed_rdf', 'fb_disable_feed', 1);
add_action('do_feed_rss', 'fb_disable_feed', 1);
add_action('do_feed_rss2', 'fb_disable_feed', 1);
add_action('do_feed_atom', 'fb_disable_feed', 1);

/** ============================================
 * Disable the REST API.
 * =============================================
 */
add_filter('rest_enabled', '__return_false');

/**
 * Disabling REST API events
 * 
 * !If you want to disable Rest Api completely, uncomment this block
 */
/*remove_action( 'init','rest_api_init' );
            remove_action( 'rest_api_init', 'rest_api_default_filters', 10, 1 );
            remove_action( 'parse_request', 'rest_api_loaded' );*/

/**
 * Remove the REST API-related links from the page header.
 */
remove_action('wp_head', 'rest_output_link_wp_head', 10, 0);
remove_action('template_redirect', 'rest_output_link_header', 11, 0);

/**
 * Remove the REST API-related cookies.
 */
remove_action('auth_cookie_malformed', 'rest_cookie_collect_status');
remove_action('auth_cookie_expired', 'rest_cookie_collect_status');
remove_action('auth_cookie_bad_username', 'rest_cookie_collect_status');
remove_action('auth_cookie_bad_hash', 'rest_cookie_collect_status');
remove_action('auth_cookie_valid', 'rest_cookie_collect_status');

/**
 * Remove the REST API-related filters.
 */
remove_filter('rest_authentication_errors', 'rest_cookie_check_errors', 100);

/**
 * Remove the REST API-related oEmbed functionality.
 */
remove_action('rest_api_init', 'wp_oembed_register_route');
remove_filter('rest_pre_serve_request', '_oembed_rest_pre_serve_request', 10, 4);
remove_action('wp_head', 'wp_oembed_add_discovery_links', 10);
remove_action('wp_head', 'wp_oembed_add_host_js');

/** ================================================
 * Disable emoji support.
 * =================================================
 */
function disable_emojis_tinymce($plugins)
{
    if (is_array($plugins)) {
        return array_diff($plugins, array('wpemoji'));
    } else {
        return array();
    }
}

function disable_wp_emojis()
{
    // Remove emojis from the head section of the site
    remove_action('wp_head', 'print_emoji_detection_script', 7);
    remove_action('wp_print_styles', 'print_emoji_styles');

    // Remove emojis from the content of posts, pages, and comments
    remove_filter('the_content_feed', 'wp_staticize_emoji');
    remove_filter('comment_text_rss', 'wp_staticize_emoji');
    remove_filter('wp_mail', 'wp_staticize_emoji_for_email');

    // Remove emojis from the TinyMCE editor
    add_filter('tiny_mce_plugins', 'disable_emojis_tinymce');
}

add_action('init', 'disable_wp_emojis');

/** ==================================================
 * MINIFY HTML OUTPUT
 * ===================================================
 */
function mcleaner_init_minify_html()
{
    ob_start('mcleaner_minify_html_output');
}
add_action('init', 'mcleaner_init_minify_html', 1);

function mcleaner_minify_html_output($buffer)
{
    if (substr(ltrim($buffer), 0, 5) == '<?xml')
        return ($buffer);
    $minify_javascript = get_option('minify_javascript');
    $minify_html_comments = get_option('minify_html_comments');
    $minify_html_utf8 = get_option('minify_html_utf8');
    if ($minify_html_utf8 == 'yes' && mb_detect_encoding($buffer, 'UTF-8', true))
        $mod = '/u';
    else
        $mod = '/s';
    $buffer = str_replace(array(chr(13) . chr(10), chr(9)), array(chr(10), ''), $buffer);
    $buffer = str_ireplace(array('<script', '/script>', '<pre', '/pre>', '<textarea', '/textarea>', '<style', '/style>'), array('M1N1FY-ST4RT<script', '/script>M1N1FY-3ND', 'M1N1FY-ST4RT<pre', '/pre>M1N1FY-3ND', 'M1N1FY-ST4RT<textarea', '/textarea>M1N1FY-3ND', 'M1N1FY-ST4RT<style', '/style>M1N1FY-3ND'), $buffer);
    $split = explode('M1N1FY-3ND', $buffer);
    $buffer = '';
    for ($i = 0; $i < count($split); $i++) {
        $ii = strpos($split[$i], 'M1N1FY-ST4RT');
        if ($ii !== false) {
            $process = substr($split[$i], 0, $ii);
            $asis = substr($split[$i], $ii + 12);
            if (substr($asis, 0, 7) == '<script') {
                $split2 = explode(chr(10), $asis);
                $asis = '';
                for ($iii = 0; $iii < count($split2); $iii++) {
                    if ($split2[$iii])
                        $asis .= trim($split2[$iii]) . chr(10);
                    if ($minify_javascript != 'no')
                        if (strpos($split2[$iii], '//') !== false && substr(trim($split2[$iii]), -1) == ';')
                            $asis .= chr(10);
                }
                if ($asis)
                    $asis = substr($asis, 0, -1);
                if ($minify_html_comments != 'no')
                    $asis = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $asis);
                if ($minify_javascript != 'no')
                    $asis = str_replace(array(';' . chr(10), '>' . chr(10), '{' . chr(10), '}' . chr(10), ',' . chr(10)), array(';', '>', '{', '}', ','), $asis);
            } else if (substr($asis, 0, 6) == '<style') {
                $asis = preg_replace(array('/\>[^\S ]+' . $mod, '/[^\S ]+\<' . $mod, '/(\s)+' . $mod), array('>', '<', '\\1'), $asis);
                if ($minify_html_comments != 'no')
                    $asis = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $asis);
                $asis = str_replace(array(chr(10), ' {', '{ ', ' }', '} ', '( ', ' )', ' :', ': ', ' ;', '; ', ' ,', ', ', ';}'), array('', '{', '{', '}', '}', '(', ')', ':', ':', ';', ';', ',', ',', '}'), $asis);
            }
        } else {
            $process = $split[$i];
            $asis = '';
        }
        $process = preg_replace(array('/\>[^\S ]+' . $mod, '/[^\S ]+\<' . $mod, '/(\s)+' . $mod), array('>', '<', '\\1'), $process);
        if ($minify_html_comments != 'no')
            $process = preg_replace('/<!--(?!\s*(?:\[if [^\]]+]|<!|>))(?:(?!-->).)*-->' . $mod, '', $process);
        $buffer .= $process . $asis;
    }
    $buffer = str_replace(array(chr(10) . '<script', chr(10) . '<style', '*/' . chr(10), 'M1N1FY-ST4RT'), array('<script', '<style', '*/', ''), $buffer);
    $minify_html_xhtml = get_option('minify_html_xhtml');
    $minify_html_relative = get_option('minify_html_relative');
    $minify_html_scheme = get_option('minify_html_scheme');
    if ($minify_html_xhtml == 'yes' && strtolower(substr(ltrim($buffer), 0, 15)) == '<!doctype html>')
        $buffer = str_replace(' />', '>', $buffer);
    if ($minify_html_relative == 'yes')
        $buffer = str_replace(array('https://' . $_SERVER['HTTP_HOST'] . '/', 'http://' . $_SERVER['HTTP_HOST'] . '/', '//' . $_SERVER['HTTP_HOST'] . '/'), array('/', '/', '/'), $buffer);
    if ($minify_html_scheme == 'yes')
        $buffer = str_replace(array('http://', 'https://'), '//', $buffer);
    return ($buffer);
}