diff --git a/WPS-Cache/includes/advanced-cache-template.php b/WPS-Cache/includes/advanced-cache-template.php
index 4c95566..b80661b 100644
--- a/WPS-Cache/includes/advanced-cache-template.php
+++ b/WPS-Cache/includes/advanced-cache-template.php
@@ -4,6 +4,7 @@
  * WPS Cache - Advanced Cache Drop-in
  * Supports Query Strings via hashed filenames.
  * Supports Mobile Cache Separation.
+ * Supports pre-compressed Gzip serving.
  */
 
 if (!defined("ABSPATH")) {
@@ -16,8 +17,23 @@
 
 class WPSAdvancedCache
 {
-    private const CACHE_LIFETIME = 3600;
-    private const COOKIE_HEADER = "wordpress_logged_in_";
+    // PHP 8.3: typed class constants
+    private const int    DEFAULT_CACHE_LIFETIME = 3600;
+    private const string COOKIE_HEADER          = "wordpress_logged_in_";
+
+    private int $cacheLifetime;
+
+    public function __construct()
+    {
+        // Load plugin-written config so the drop-in respects the admin setting
+        // without bootstrapping WordPress.
+        $configFile = WP_CONTENT_DIR . "/cache/wps-cache/config.php";
+        $config     = is_file($configFile) ? (@include $configFile) : [];
+        $config     = is_array($config) ? $config : [];
+        $this->cacheLifetime = isset($config["cache_lifetime"])
+            ? (int) $config["cache_lifetime"]
+            : self::DEFAULT_CACHE_LIFETIME;
+    }
 
     public function execute(): void
     {
@@ -27,9 +43,10 @@ public function execute(): void
 
         $file = $this->getCacheFilePath();
 
-        if (file_exists($file)) {
+        // is_file() is faster than file_exists() – it skips the directory check.
+        if (is_file($file)) {
             $mtime = filemtime($file);
-            if (time() - $mtime > self::CACHE_LIFETIME) {
+            if (time() - $mtime > $this->cacheLifetime) {
                 return;
             }
             $this->serve($file, $mtime);
@@ -46,9 +63,10 @@ private function shouldBypass(): bool
         // We now rely on the file existence check.
         // If query params exist but no file matches the hash, it falls through to WP.
 
-        foreach ($_COOKIE as $key => $value) {
+        foreach ($_COOKIE as $key => $_value) {
+            // PHP 8.0+: str_starts_with() avoids the strpos() === 0 idiom.
             if (
-                strpos($key, self::COOKIE_HEADER) === 0 ||
+                str_starts_with($key, self::COOKIE_HEADER) ||
                 $key === "wp-postpass_" ||
                 $key === "comment_author_"
             ) {
@@ -58,10 +76,8 @@ private function shouldBypass(): bool
 
         // Special paths
         $uri = $_SERVER["REQUEST_URI"] ?? "/";
-        if (
-            strpos($uri, "/wp-admin") !== false ||
-            strpos($uri, "/xmlrpc.php") !== false
-        ) {
+        // PHP 8.0+: str_contains() is cleaner and avoids !== false checks.
+        if (str_contains($uri, "/wp-admin") || str_contains($uri, "/xmlrpc.php")) {
             return true;
         }
 
@@ -75,62 +91,39 @@ private function getCacheFilePath(): string
             "",
             $_SERVER["HTTP_HOST"] ?? "unknown",
         );
-        $uri = $_SERVER["REQUEST_URI"] ?? "/";
-
-        $path = parse_url($uri, PHP_URL_PATH);
-        // $path = str_replace("..", "", $path); // Security
-        $path = $this->sanitizePath($path);
+        $uri  = $_SERVER["REQUEST_URI"] ?? "/";
+        $path = $this->sanitizePath(parse_url($uri, PHP_URL_PATH) ?: "/");
 
-        if (
-            substr($path, -1) !== "/" &&
-            !preg_match('/\.[a-z0-9]{2,4}$/i', $path)
-        ) {
+        // PHP 8.0+: str_ends_with() instead of substr($path, -1) !== "/".
+        if (!str_ends_with($path, "/") && !preg_match('/\.[a-z0-9]{2,4}$/i', $path)) {
             $path .= "/";
         }
 
-        // Determine Mobile Suffix
         $suffix = $this->getMobileSuffix();
 
-        // Determine Filename
         $query = parse_url($uri, PHP_URL_QUERY);
         if ($query) {
             parse_str($query, $queryParams);
             ksort($queryParams);
-            // Append suffix to query-string based filenames
-            $filename =
-                "index" .
-                $suffix .
-                "-" .
-                md5(http_build_query($queryParams)) .
-                ".html";
+            $filename = "index" . $suffix . "-" . md5(http_build_query($queryParams)) . ".html";
         } else {
-            // Append suffix to standard filenames
             $filename = "index" . $suffix . ".html";
         }
 
-        return WP_CONTENT_DIR .
-            "/cache/wps-cache/html/" .
-            $host .
-            $path .
-            $filename;
+        return WP_CONTENT_DIR . "/cache/wps-cache/html/" . $host . $path . $filename;
     }
 
     /**
      * Efficiently detects mobile devices based on User-Agent.
-     * Must match logic in HTMLCache.php
+     * Must match logic in HTMLCache.php.
      */
     private function getMobileSuffix(): string
     {
         $ua = $_SERVER["HTTP_USER_AGENT"] ?? "";
-        if (empty($ua)) {
+        if ($ua === "") {
             return "";
         }
-        if (
-            preg_match(
-                "/(Mobile|Android|Silk\/|Kindle|BlackBerry|Opera Mini|Opera Mobi)/i",
-                $ua,
-            )
-        ) {
+        if (preg_match("/(Mobile|Android|Silk\/|Kindle|BlackBerry|Opera Mini|Opera Mobi)/i", $ua)) {
             return "-mobile";
         }
         return "";
@@ -138,8 +131,8 @@ private function getMobileSuffix(): string
 
     private function sanitizePath(string $path): string
     {
-        $path = str_replace(chr(0), "", $path);
-        $parts = explode("/", $path);
+        $path     = str_replace(chr(0), "", $path);
+        $parts    = explode("/", $path);
         $safeParts = [];
         foreach ($parts as $part) {
             if ($part === "" || $part === ".") {
@@ -156,7 +149,12 @@ private function sanitizePath(string $path): string
 
     private function serve(string $file, int $mtime): void
     {
-        $etag = '"' . $mtime . '"';
+        $fileSize = (int) filesize($file);
+        // Apache-style ETag combining last-modified time and file size.
+        $etag         = sprintf('"%x-%x"', $mtime, $fileSize);
+        $lastModified = gmdate("D, d M Y H:i:s", $mtime) . " GMT";
+
+        // ETag-based conditional request (strong validator).
         if (
             isset($_SERVER["HTTP_IF_NONE_MATCH"]) &&
             trim($_SERVER["HTTP_IF_NONE_MATCH"]) === $etag
@@ -165,14 +163,47 @@ private function serve(string $file, int $mtime): void
             exit();
         }
 
+        // Date-based conditional request (weak validator).
+        if (isset($_SERVER["HTTP_IF_MODIFIED_SINCE"])) {
+            $ims = strtotime($_SERVER["HTTP_IF_MODIFIED_SINCE"]);
+            if ($ims !== false && $mtime < $ims) {
+                header("HTTP/1.1 304 Not Modified");
+                exit();
+            }
+        }
+
+        // Serve a pre-compressed gzip file when the client accepts it and the
+        // file exists.  This eliminates on-the-fly compression overhead.
+        $acceptEncoding = $_SERVER["HTTP_ACCEPT_ENCODING"] ?? "";
+        $gzFile         = $file . ".gz";
+        $useGzip        = str_contains($acceptEncoding, "gzip") && is_file($gzFile);
+
+        // Prevent the web server / PHP from double-compressing the response.
+        if ($useGzip && function_exists("ini_set")) {
+            ini_set("zlib.output_compression", "0");
+        }
+
         header("Content-Type: text/html; charset=UTF-8");
-        header("Cache-Control: public, max-age=3600");
+        header("Cache-Control: public, max-age=" . $this->cacheLifetime);
         header("ETag: " . $etag);
+        header("Last-Modified: " . $lastModified);
+        header("Expires: " . gmdate("D, d M Y H:i:s", time() + $this->cacheLifetime) . " GMT");
+        // Always advertise Vary so CDNs/proxies store separate copies per encoding.
+        header("Vary: Accept-Encoding");
         header("X-WPS-Cache: HIT");
 
-        readfile($file);
+        if ($useGzip) {
+            $gzSize = (int) filesize($gzFile);
+            header("Content-Encoding: gzip");
+            header("Content-Length: " . $gzSize);
+            readfile($gzFile);
+        } else {
+            header("Content-Length: " . $fileSize);
+            readfile($file);
+        }
+
         exit();
     }
 }
 
-new WPSAdvancedCache()->execute();
+(new WPSAdvancedCache())->execute();
diff --git a/WPS-Cache/src/Cache/Drivers/AbstractCacheDriver.php b/WPS-Cache/src/Cache/Drivers/AbstractCacheDriver.php
index 4d7442e..311cd78 100644
--- a/WPS-Cache/src/Cache/Drivers/AbstractCacheDriver.php
+++ b/WPS-Cache/src/Cache/Drivers/AbstractCacheDriver.php
@@ -94,7 +94,7 @@ protected function atomicWrite(string $filepath, string $content): bool
             return false;
         }
 
-        if (file_put_contents($temp_file, $content) === false) {
+        if (file_put_contents($temp_file, $content, LOCK_EX) === false) {
             $this->logError("Failed to write content to $temp_file");
             @unlink($temp_file);
             return false;
diff --git a/WPS-Cache/src/Cache/Drivers/HTMLCache.php b/WPS-Cache/src/Cache/Drivers/HTMLCache.php
index e1ec89e..6ec291a 100644
--- a/WPS-Cache/src/Cache/Drivers/HTMLCache.php
+++ b/WPS-Cache/src/Cache/Drivers/HTMLCache.php
@@ -21,7 +21,8 @@ final class HTMLCache extends AbstractCacheDriver
     private ?CommerceManager $commerceManager;
 
     // Optimization: Use hash map for O(1) lookups
-    private const BYPASS_PARAMS = [
+    // PHP 8.3: typed class constants
+    private const array BYPASS_PARAMS = [
         "add-to-cart" => true,
         "wp_nonce" => true,
         "preview" => true,
@@ -29,12 +30,12 @@ final class HTMLCache extends AbstractCacheDriver
     ];
 
     // Sentinel: Limits to prevent Cache DoS (Disk Exhaustion)
-    private const MAX_QUERY_LEN = 512;
-    private const MAX_QUERY_PARAMS = 10;
+    private const int MAX_QUERY_LEN    = 512;
+    private const int MAX_QUERY_PARAMS = 10;
 
     // SOTA: Explicitly ignore static extensions to prevent "Soft 404" caching
     // Optimization: Use hash map for O(1) lookups
-    private const IGNORED_EXTENSIONS = [
+    private const array IGNORED_EXTENSIONS = [
         "xml" => true,
         "json" => true,
         "map" => true,
@@ -161,6 +162,18 @@ public function processOutput(string $buffer): string
             return $buffer;
         }
 
+        // Only cache actual HTML responses; skip JSON/XML/feeds etc.
+        $contentType = "";
+        foreach (headers_list() as $h) {
+            if (stripos($h, "Content-Type:") === 0) {
+                $contentType = $h;
+                break;
+            }
+        }
+        if ($contentType !== "" && stripos($contentType, "text/html") === false) {
+            return $buffer;
+        }
+
         // --- PHASE 1: DOM MANIPULATION (Robust & Safe) ---
         $useDomPipeline =
             !empty($this->settings["remove_unused_css"]) ||
@@ -170,7 +183,9 @@ public function processOutput(string $buffer): string
         $content = $buffer;
 
         if ($useDomPipeline) {
-            libxml_use_internal_errors(true);
+            // Save and restore the previous libxml error-handling state so we
+            // don't permanently silence errors for the rest of the request.
+            $prevLibxmlErrors = libxml_use_internal_errors(true);
             $dom = new DOMDocument();
             // Hack: force UTF-8
             @$dom->loadHTML(
@@ -178,6 +193,7 @@ public function processOutput(string $buffer): string
                 LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD,
             );
             libxml_clear_errors();
+            libxml_use_internal_errors($prevLibxmlErrors);
 
             // 1. Remove Unused CSS (DOM)
             if (!empty($this->settings["remove_unused_css"])) {
@@ -227,6 +243,11 @@ public function processOutput(string $buffer): string
         } catch (\Throwable $e) {
         }
 
+        // 6. HTML Minification – strip HTML comments and collapse inter-tag
+        //    whitespace.  Done after all other processors to avoid interfering
+        //    with DOM-based pipelines above.
+        $content = $this->minifyHtml($content);
+
         // Add Timestamp & Signature
         $deviceType = $this->getMobileSuffix() ? "Mobile" : "Desktop";
         $content .= sprintf(
@@ -240,6 +261,35 @@ public function processOutput(string $buffer): string
         return $content;
     }
 
+    /**
+     * Lightweight HTML minifier.
+     *
+     * - Strips HTML comments (preserves IE conditional comments).
+     * - Collapses whitespace-only gaps between block-level elements.
+     *
+     * Intentionally conservative: it does NOT touch content inside
+     * <pre>, <script>, <style>, or <textarea> to avoid breaking those blocks.
+     */
+    private function minifyHtml(string $html): string
+    {
+        // 1. Remove HTML comments except IE conditionals (<!--[if …]> … <![endif]-->)
+        $result = preg_replace('/<!--(?!\[if\s)[\s\S]*?-->/u', '', $html);
+        // Guard: if regex failed (e.g. invalid UTF-8), keep original.
+        if ($result !== null) {
+            $html = $result;
+        }
+
+        // 2. Collapse runs of whitespace between tags to a single newline.
+        //    Using \s+ rather than a more aggressive trim to preserve
+        //    inline-element spacing.
+        $result = preg_replace('/>\s{2,}</u', ">\n<", $html);
+        if ($result !== null) {
+            $html = $result;
+        }
+
+        return $html;
+    }
+
     private function writeCacheFile(string $content): void
     {
         $host = $_SERVER["HTTP_HOST"] ?? "unknown";
@@ -252,18 +302,18 @@ private function writeCacheFile(string $content): void
             $host = "unknown";
         }
 
-        $uri = $_SERVER["REQUEST_URI"] ?? "/";
+        $uri  = $_SERVER["REQUEST_URI"] ?? "/";
         $path = $this->sanitizePath(parse_url($uri, PHP_URL_PATH));
 
         if (
-            substr($path, -1) !== "/" &&
+            !str_ends_with($path, "/") &&
             !preg_match('/\.[a-z0-9]{2,4}$/i', $path)
         ) {
             $path .= "/";
         }
 
         $suffix = $this->getMobileSuffix();
-        $query = parse_url($uri, PHP_URL_QUERY);
+        $query  = parse_url($uri, PHP_URL_QUERY);
 
         if ($query) {
             parse_str($query, $queryParams);
@@ -279,11 +329,22 @@ private function writeCacheFile(string $content): void
         }
 
         $fullPath = $this->cacheDir . $host . $path;
-        if (substr($fullPath, -1) !== "/") {
+        if (!str_ends_with($fullPath, "/")) {
             $fullPath .= "/";
         }
 
-        $this->atomicWrite($fullPath . $filename, $content);
+        $htmlFile = $fullPath . $filename;
+        $this->atomicWrite($htmlFile, $content);
+
+        // Write a pre-compressed gzip version alongside the plain file so the
+        // advanced-cache drop-in can serve it directly, eliminating per-request
+        // compression overhead entirely.
+        if (function_exists("gzencode")) {
+            $compressed = gzencode($content, 6);
+            if ($compressed !== false) {
+                $this->atomicWrite($htmlFile . ".gz", $compressed);
+            }
+        }
     }
 
     private function getMobileSuffix(): string
diff --git a/WPS-Cache/src/Plugin.php b/WPS-Cache/src/Plugin.php
index 9af3f7a..e54181e 100644
--- a/WPS-Cache/src/Plugin.php
+++ b/WPS-Cache/src/Plugin.php
@@ -271,6 +271,15 @@ public function activate(): void
         $this->enableWPCacheConstant();
         $this->installAdvancedCache();
         $this->setupDefaultSettings();
+        // Write the runtime config file read by the advanced-cache drop-in so
+        // it picks up admin-configured settings (e.g. cache_lifetime) without
+        // needing to bootstrap WordPress.
+        $settings = get_option("wpsc_settings", self::DEFAULT_SETTINGS);
+        $settings = array_merge(
+            self::DEFAULT_SETTINGS,
+            is_array($settings) ? $settings : [],
+        );
+        $this->writeAdvancedCacheConfig($settings);
         $this->scheduleMaintenance();
         $this->serverManager->applyConfiguration();
         flush_rewrite_rules();
@@ -325,6 +334,7 @@ public function handleManualDbCleanup(): void
 
     public function refreshServerConfig(array $settings): void
     {
+        $this->writeAdvancedCacheConfig($settings);
         if ($settings["html_cache"] ?? false) {
             $this->serverManager->applyConfiguration();
         } else {
@@ -332,6 +342,26 @@ public function refreshServerConfig(array $settings): void
         }
     }
 
+    /**
+     * Writes a small PHP config file into the cache directory so the
+     * advanced-cache drop-in can read admin settings (e.g. cache_lifetime)
+     * without bootstrapping WordPress on every request.
+     */
+    private function writeAdvancedCacheConfig(array $settings): void
+    {
+        if (!defined("WPSC_CACHE_DIR")) {
+            return;
+        }
+        $config = [
+            "cache_lifetime" => (int) ($settings["cache_lifetime"] ?? 3600),
+        ];
+        $content  = "<?php\nreturn " . var_export($config, true) . ";\n";
+        $written  = file_put_contents(WPSC_CACHE_DIR . "config.php", $content, LOCK_EX);
+        if ($written === false && defined("WP_DEBUG") && WP_DEBUG) {
+            error_log("WPS-Cache: Failed to write advanced-cache config file.");
+        }
+    }
+
     public function getDatabaseOptimizer(): DatabaseOptimizer
     {
         return $this->databaseOptimizer;
@@ -440,9 +470,11 @@ private function toggleWPCache(bool $enable): bool
 
     private function installAdvancedCache(): void
     {
-        $src = WPSC_PLUGIN_DIR . "includes/advanced-cache-template.php";
+        $src  = WPSC_PLUGIN_DIR . "includes/advanced-cache-template.php";
         $dest = WP_CONTENT_DIR . "/advanced-cache.php";
-        if (file_exists($src) && !file_exists($dest)) {
+        // Always overwrite on activation so the drop-in stays in sync with
+        // the installed plugin version.
+        if (file_exists($src)) {
             @copy($src, $dest);
         }
     }