diff --git a/package.json b/package.json
index 2351ed2..d6289c4 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "scripts": {
     "build": "node esbuild.config.js",
     "dev": "npm run build && npm run start",
-    "lint": "eslint --no-error-on-unmatched-pattern src/**/*.js src/*.js tests/**/*.test.js tests/**/*.js utils/**/*.js",
+    "lint": "eslint --no-error-on-unmatched-pattern src/**/*.js src/*.js tests/**/*.test.js tests/**/*.js tests/*.test.js tests/*.js utils/**/*.js utils/*.js",
     "lint:fix": "npm run lint -- --fix",
     "start": "node dist/svr.js",
     "test": "jest"
diff --git a/src/utils/forbiddenPaths.js b/src/utils/forbiddenPaths.js
index b91a4f7..d2d4007 100644
--- a/src/utils/forbiddenPaths.js
+++ b/src/utils/forbiddenPaths.js
@@ -22,57 +22,50 @@ function getInitializePath(to) {
   }
 }
 
-// Function to check if URL path name is a forbidden path.
 function isForbiddenPath(decodedHref, match) {
   const forbiddenPath = forbiddenPaths[match];
   if (!forbiddenPath) return false;
+
+  const isWin32 = os.platform() === "win32";
+  const decodedHrefLower = isWin32 ? decodedHref.toLowerCase() : null;
+
   if (typeof forbiddenPath === "string") {
-    return (
-      decodedHref === forbiddenPath ||
-      (os.platform() === "win32" &&
-        decodedHref.toLowerCase() === forbiddenPath.toLowerCase())
-    );
+    return isWin32
+      ? decodedHrefLower === forbiddenPath.toLowerCase()
+      : decodedHref === forbiddenPath;
   }
+
   if (typeof forbiddenPath === "object") {
-    return forbiddenPath.some((forbiddenPathSingle) => {
-      return (
-        decodedHref === forbiddenPathSingle ||
-        (os.platform() === "win32" &&
-          decodedHref.toLowerCase() === forbiddenPathSingle.toLowerCase())
-      );
-    });
+    return isWin32
+      ? forbiddenPath.some((path) => decodedHrefLower === path.toLowerCase())
+      : forbiddenPath.includes(decodedHref);
   }
+
   return false;
 }
 
-// Function to check if URL path name is index of one of defined forbidden paths.
 function isIndexOfForbiddenPath(decodedHref, match) {
   const forbiddenPath = forbiddenPaths[match];
   if (!forbiddenPath) return false;
+
+  const isWin32 = os.platform() === "win32";
+  const decodedHrefLower = isWin32 ? decodedHref.toLowerCase() : null;
+
   if (typeof forbiddenPath === "string") {
-    return (
-      decodedHref === forbiddenPath ||
-      decodedHref.indexOf(forbiddenPath + "/") === 0 ||
-      (os.platform() === "win32" &&
-        (decodedHref.toLowerCase() === forbiddenPath.toLowerCase() ||
-          decodedHref
-            .toLowerCase()
-            .indexOf(forbiddenPath.toLowerCase() + "/") === 0))
-    );
+    const forbiddenPathLower = isWin32 ? forbiddenPath.toLowerCase() : null;
+    return isWin32
+      ? decodedHrefLower.indexOf(forbiddenPathLower) == 0
+      : decodedHref.indexOf(forbiddenPath) == 0;
   }
+
   if (typeof forbiddenPath === "object") {
-    return forbiddenPath.some((forbiddenPathSingle) => {
-      return (
-        decodedHref === forbiddenPathSingle ||
-        decodedHref.indexOf(forbiddenPathSingle + "/") === 0 ||
-        (os.platform() === "win32" &&
-          (decodedHref.toLowerCase() === forbiddenPathSingle.toLowerCase() ||
-            decodedHref
-              .toLowerCase()
-              .indexOf(forbiddenPathSingle.toLowerCase() + "/") === 0))
-      );
-    });
+    return isWin32
+      ? forbiddenPath.some(
+          (path) => decodedHrefLower.indexOf(path.toLowerCase()) == 0,
+        )
+      : forbiddenPath.some((path) => decodedHref.indexOf(path) == 0);
   }
+
   return false;
 }
 
diff --git a/src/utils/legacyModWrapper.js b/src/utils/legacyModWrapper.js
index 12994e0..2ce6504 100644
--- a/src/utils/legacyModWrapper.js
+++ b/src/utils/legacyModWrapper.js
@@ -13,6 +13,7 @@ module.exports = (legacyMod) => {
   let middleware = (req, res, logFacilities, config, next) => {
     let ext = req.parsedURL.pathname.match(/[^/]\.([^.]+)$/);
     if (!ext) ext = "";
+    else ext = ext[1].toLowerCase();
 
     // Function to parse incoming POST data from the request
     const parsePostData = (options, callback) => {
diff --git a/src/utils/matchHostname.js b/src/utils/matchHostname.js
index b2c8c46..36b3ce4 100644
--- a/src/utils/matchHostname.js
+++ b/src/utils/matchHostname.js
@@ -1,17 +1,17 @@
 function matchHostname(hostname, reqHostname) {
-  if (typeof hostname == "undefined" || hostname == "*") {
+  if (typeof hostname === "undefined" || hostname === "*") {
     return true;
-  } else if (reqHostname && hostname.indexOf("*.") == 0 && hostname != "*.") {
+  } else if (reqHostname && hostname.indexOf("*.") == 0 && hostname !== "*.") {
     const hostnamesRoot = hostname.substring(2);
     if (
-      reqHostname == hostnamesRoot ||
+      reqHostname === hostnamesRoot ||
       (reqHostname.length > hostnamesRoot.length &&
-        reqHostname.indexOf("." + hostnamesRoot) ==
+        reqHostname.indexOf("." + hostnamesRoot) ===
           reqHostname.length - hostnamesRoot.length - 1)
     ) {
       return true;
     }
-  } else if (reqHostname && reqHostname == hostname) {
+  } else if (reqHostname && reqHostname === hostname) {
     return true;
   }
   return false;
diff --git a/src/utils/sizify.js b/src/utils/sizify.js
index 203746c..688ed54 100644
--- a/src/utils/sizify.js
+++ b/src/utils/sizify.js
@@ -1,26 +1,25 @@
 function sizify(bytes, addI) {
-  if (bytes == 0) return "0";
+  if (bytes === 0) return "0";
   if (bytes < 0) bytes = -bytes;
+
   const prefixes = ["", "K", "M", "G", "T", "P", "E", "Z", "Y", "R", "Q"];
-  let prefixIndex = Math.floor(
-    Math.log2 ? Math.log2(bytes) / 10 : Math.log(bytes) / (Math.log(2) * 10),
+  const prefixIndex = Math.min(
+    Math.floor(Math.log2(bytes) / 10),
+    prefixes.length - 1,
   );
-  if (prefixIndex >= prefixes.length - 1) prefixIndex = prefixes.length - 1;
-  let prefixIndexTranslated = Math.pow(2, 10 * prefixIndex);
-  let decimalPoints =
-    2 -
-    Math.floor(
-      Math.log10
-        ? Math.log10(bytes / prefixIndexTranslated)
-        : Math.log(bytes / prefixIndexTranslated) / Math.log(10),
-    );
-  if (decimalPoints < 0) decimalPoints = 0;
-  return (
+  const prefixIndexTranslated = Math.pow(2, 10 * prefixIndex);
+  const decimalPoints = Math.max(
+    2 - Math.floor(Math.log10(bytes / prefixIndexTranslated)),
+    0,
+  );
+
+  const size =
     Math.ceil((bytes / prefixIndexTranslated) * Math.pow(10, decimalPoints)) /
-      Math.pow(10, decimalPoints) +
-    prefixes[prefixIndex] +
-    (prefixIndex > 0 && addI ? "i" : "")
-  );
+    Math.pow(10, decimalPoints);
+  const prefix = prefixes[prefixIndex];
+  const suffix = prefixIndex > 0 && addI ? "i" : "";
+
+  return size + prefix + suffix;
 }
 
 module.exports = sizify;
diff --git a/src/utils/urlMojibakeFixer.js b/src/utils/urlMojibakeFixer.js
index f7e6c47..7fd718c 100644
--- a/src/utils/urlMojibakeFixer.js
+++ b/src/utils/urlMojibakeFixer.js
@@ -1,21 +1,16 @@
 // Node.JS mojibake URL fixing function
 function fixNodeMojibakeURL(string) {
-  var encoded = "";
-
-  //Encode URLs
-  Buffer.from(string, "latin1").forEach((value) => {
-    if (value > 127) {
-      encoded +=
-        "%" + (value < 16 ? "0" : "") + value.toString(16).toUpperCase();
-    } else {
-      encoded += String.fromCodePoint(value);
-    }
-  });
-
-  //Upper case the URL encodings
-  return encoded.replace(/%[0-9a-f-A-F]{2}/g, (match) => {
-    return match.toUpperCase();
-  });
+  return Buffer.from(string, "latin1")
+    .reduce((result, value) => {
+      if (value > 127) {
+        result +=
+          "%" + (value < 16 ? "0" : "") + value.toString(16).toUpperCase();
+      } else {
+        result += String.fromCharCode(value);
+      }
+      return result;
+    }, "")
+    .replace(/%[0-9a-f]{2}/gi, (match) => match.toUpperCase());
 }
 
 module.exports = fixNodeMojibakeURL;
diff --git a/src/utils/urlParser.js b/src/utils/urlParser.js
index 1aed5b0..cdc4400 100644
--- a/src/utils/urlParser.js
+++ b/src/utils/urlParser.js
@@ -1,6 +1,6 @@
 const url = require("url");
 
-// SVR.JS URL parser function (needed only for SVR.JS 2.x and 3.x mods)
+// SVR.JS URL parser function (compatible with legacy Node.JS URL parsing function)
 function parseURL(uri, prepend) {
   // Replace newline characters with its respective URL encodings
   uri = uri.replace(/\r/g, "%0D").replace(/\n/g, "%0A");
@@ -13,7 +13,7 @@ function parseURL(uri, prepend) {
 
   // Parse the URL using regular expression
   let parsedURI = uri.match(
-    /^(?:([^:]+:)(\/\/)?)?(?:([^@/?#*]+)@)?([^:/?#*]+|\[[^*]\/]\])?(?::([0-9]+))?(\*|\/[^?#]*)?(\?[^#]*)?(#[\S\s]*)?/,
+    /^(?:([^:]+:)(\/\/)?)?(?:([^@/?#*]+)@)?([^:/?#*]+|\[[^*\]/]\])?(?::([0-9]+))?(\*|\/[^?#]*)?(\?[^#]*)?(#[\S\s]*)?/,
   );
   // Match 1: protocol
   // Match 2: slashes after protocol
diff --git a/src/utils/urlSanitizer.js b/src/utils/urlSanitizer.js
index 904e2de..b2ada45 100644
--- a/src/utils/urlSanitizer.js
+++ b/src/utils/urlSanitizer.js
@@ -1,43 +1,50 @@
 // SVR.JS path sanitizer function
 function sanitizeURL(resource, allowDoubleSlashes) {
-  if (resource == "*" || resource == "") return resource;
+  if (resource === "*" || resource === "") return resource;
+
   // Remove null characters
   resource = resource.replace(/%00|\0/g, "");
+
   // Check if URL is malformed (e.g. %c0%af or %u002f or simply %as)
   if (resource.match(/%(?:c[01]|f[ef]|(?![0-9a-f]{2}).{2}|.{0,1}$)/i))
     throw new URIError("URI malformed");
+
   // Decode URL-encoded characters while preserving certain characters
   resource = resource.replace(/%([0-9a-f]{2})/gi, (match, hex) => {
     const decodedChar = String.fromCharCode(parseInt(hex, 16));
-    return /(?!["<>^`{|}?#%])[!-~]/.test(decodedChar) ? decodedChar : "%" + hex;
+    return /[!$&-;=@-\]_a-z~]/.test(decodedChar) ? decodedChar : match;
   });
+
   // Encode certain characters
-  resource = resource.replace(/[<>^`{|}]]/g, (character) => {
+  resource = resource.replace(/[<>^`{|}]/g, (character) => {
     const charCode = character.charCodeAt(0);
     return (
       "%" + (charCode < 16 ? "0" : "") + charCode.toString(16).toUpperCase()
     );
   });
-  let sanitizedResource = resource;
+
   // Ensure the resource starts with a slash
-  if (resource[0] != "/") sanitizedResource = "/" + sanitizedResource;
+  if (resource[0] !== "/") resource = "/" + resource;
+
   // Convert backslashes to slashes and handle duplicate slashes
-  sanitizedResource = sanitizedResource
+  resource = resource
     .replace(/\\/g, "/")
     .replace(allowDoubleSlashes ? /\/{3,}/g : /\/+/g, "/");
-  // Handle relative navigation (e.g., "/./", "/../", "../", "./"), also remove trailing dots in paths
-  sanitizedResource = sanitizedResource
+
+  // Handle relative navigation (e.g., "/./", "/../", "../", "./") and remove trailing dots in paths
+  resource = resource
     .replace(/\/\.(?:\.{2,})?(?=\/|$)/g, "")
     .replace(/([^./])\.+(?=\/|$)/g, "$1");
-  while (sanitizedResource.match(/\/(?!\.\.\/)[^/]+\/\.\.(?=\/|$)/)) {
-    sanitizedResource = sanitizedResource.replace(
-      /\/(?!\.\.\/)[^/]+\/\.\.(?=\/|$)/g,
-      "",
-    );
+
+  // Remove remaining "../"
+  while (resource.match(/\/(?!\.\.\/)[^/]+\/\.\.(?=\/|$)/)) {
+    resource = resource.replace(/\/(?!\.\.\/)[^/]+\/\.\.(?=\/|$)/g, "");
   }
-  sanitizedResource = sanitizedResource.replace(/\/\.\.(?=\/|$)/g, "");
-  if (sanitizedResource.length == 0) return "/";
-  else return sanitizedResource;
+  resource = resource.replace(/\/\.\.(?=\/|$)/g, "");
+
+  // If the result has length of 0, return "/", else return the sanitized URL
+  if (resource.length == 0) return "/";
+  else return resource;
 }
 
 module.exports = sanitizeURL;
diff --git a/svrjs.json b/svrjs.json
index f9477da..139dafd 100644
--- a/svrjs.json
+++ b/svrjs.json
@@ -1,9 +1,11 @@
 {
-  "version": "4.0.0-beta1",
+  "version": "4.0.0-beta2",
   "name": "SVR.JS",
   "documentationURL": "https://svrjs.org/docs/tentative",
   "statisticsServerCollectEndpoint": "https://statistics.svrjs.org/collect.svr",
   "changes": [
-    "First SVR.JS 4.0.0 beta version"
+    "Fixed the bug with \"ext\" variable for .tar.gz mods.",
+    "Fixed the regular expression in the URL parser.",
+    "Optimized many functions"
   ]
 }