diff --git a/lib/error.js b/lib/error.js
index 70ccd8e..fefe46b 100644
--- a/lib/error.js
+++ b/lib/error.js
@@ -8,7 +8,7 @@
 
 'use strict';
 
-const { isPlainObject } = require('./utils');
+const { isPlainObject } = require('./utils/type-utils');
 
 /**
  * @classdesc Represents an error that occurred during video ID extraction.
diff --git a/lib/utils.js b/lib/utils/index.js
similarity index 51%
rename from lib/utils.js
rename to lib/utils/index.js
index 5c6dabd..fd9e043 100644
--- a/lib/utils.js
+++ b/lib/utils/index.js
@@ -1,41 +1,24 @@
 /**
- * Utilities module for **YTMP3** project.
+ * Main entry for `utils` module of **YTMP3-JS** project.
+ *
+ * This module provides a set of submodules for working with various utilities.
+ * These submodules are:
+ *
+ * - {@link module:utils/logger} - A submodule for logging process.
+ * - {@link module:utils/yt-urlfmt} - A submodule containing all supported YouTube URLs in regular expressions (_deprecated_).
+ * - {@link module:utils/url-utils} - A submodule for working with YouTube URLs.
+ * - {@link module:utils/type-utils} - A submodule for type checking and utility functions.
  *
  * @module    utils
+ * @requires  utils/logger
+ * @requires  utils/yt-urlfmt
+ * @requires  utils/url-utils
+ * @requires  utils/type-utils
  * @author    Ryuu Mitsuki <https://github.com/mitsuki31>
  * @license   MIT
  * @since     1.0.0
  */
 
-'use strict';
-
-const fs = require('node:fs');
-const os = require('node:os');
-const path = require('node:path');
-
-/**
- * @typedef {Function} LoggerFunc
- * @param   {string} msg - The message to be displayed.
- * @returns {void}
- * @since   1.0.0
- */
-
-/**
- * The interface of {@link module:utils~logger `logger`} object.
- *
- * @typedef  {Object} LoggerInterface
- * @property {string} INFO_PREFIX - The prefix for the info level message.
- * @property {string} DONE_PREFIX - The prefix for the done level message.
- * @property {string} DEBUG_PREFIX - The prefix for the debug level message.
- * @property {string} WARNING_PREFIX - The prefix for the warning level message.
- * @property {string} ERROR_PREFIX - The prefix for the error level message.
- * @property {LoggerFunc} info - The function to log the info level message to the console.
- * @property {LoggerFunc} done - The function to log the done level message to the console.
- * @property {LoggerFunc} debug - The function to log the debug level message to the console.
- * @property {LoggerFunc} warn - The function to log the warning level message to the console.
- * @property {LoggerFunc} error - The function to log the error level message to the console.
- * @since    1.0.0
- */
 
 /**
  * Options object for configuring the progress bar.
@@ -61,13 +44,20 @@ const path = require('node:path');
  * @since    1.0.0
  */
 
-// region Constants
+'use strict';
+
+const fs = require('node:fs');
+const os = require('node:os');
+const path = require('node:path');
 
-const FrozenProperty = {
-  writable: false,
-  configurable: false,
-  enumerable: true
-};
+// Local imports
+const Logger = require('./logger');
+const TypeUtils = require('./type-utils');
+const URLFmt = require('./yt-urlfmt');
+const URLUtils = require('./url-utils');
+
+
+// region Constants
 
 /**
  * The root directory of the project.
@@ -76,7 +66,8 @@ const FrozenProperty = {
  * @package
  * @since  1.0.0
  */
-const ROOTDIR = path.join(__dirname, '..');
+const ROOTDIR = path.join(__dirname, '..', '..');
+
 /**
  * The output directory for the downloaded audio files.
  * @type {string}
@@ -85,12 +76,14 @@ const ROOTDIR = path.join(__dirname, '..');
  * @since  1.0.0
  */
 const OUTDIR = path.join(ROOTDIR, 'download');
+
 /**
  * The home directory path for the YTMP3-JS configuration and data files.
  *
  * This path is constructed by joining the user's home directory with the `'.ytmp3-js'` folder.
  * On POSIX systems, this will typically be `"/home/<USERNAME>/.ytmp3-js"`, while on Windows systems,
- * it will be `"C:\Users\<USERNAME>\.ytmp3-js"`. For Termux Android, it will be `"/data/data/com.termux/files/home/.ytmp3-js"`.
+ * it will be `"C:\Users\<USERNAME>\.ytmp3-js"`. For Termux Android, it will be
+ * `"/data/data/com.termux/files/home/.ytmp3-js"`.
  *
  * @type {string}
  * @constant
@@ -113,6 +106,7 @@ const YTMP3_HOMEDIR = path.join(os.homedir(), '.ytmp3-js');
  */
 const LOGDIR = path.join(YTMP3_HOMEDIR, 'logs');
 
+
 // region Utilities Function
 
 /**
@@ -123,7 +117,7 @@ const LOGDIR = path.join(YTMP3_HOMEDIR, 'logs');
  * @returns {Promise<void>}
  *
  * @async
- * @public
+ * @package
  * @since  1.0.0
  */
 async function createDirIfNotExist(dirpath) {
@@ -134,7 +128,7 @@ async function createDirIfNotExist(dirpath) {
  * Similar with {@link module:utils~createDirIfNotExist `createDirIfNotExist`}
  * function, but it uses synchronous directory creation.
  *
- * @public
+ * @package
  * @since 1.0.1
  */
 function createDirIfNotExistSync(dirpath) {
@@ -157,225 +151,6 @@ function createLogFile(prefix) {
 }
 
 
-// region Type Checker
-
-/**
- * Checks if a given value is null or undefined.
- *
- * @param {any} x - The value to check.
- * @returns {boolean} - `true` if the value is null or undefined, otherwise `false`.
- *
- * @public
- * @since  1.0.0
- */
-function isNullOrUndefined(x) {
-  return (x === null || typeof x === 'undefined');
-}
-
-/**
- * Determines whether the provided value is a non-null object.
- *
- * This function returns `true` for any value that is of the object type and is not `null`, 
- * but it does not guarantee that the object is a plain object (`{}`).
- *
- * @param {any} x - The value to be checked.
- * @returns {boolean} `true` if the value is a non-null object, otherwise `false`.
- *
- * @package
- * @since    1.0.0
- * @see      {@link module:utils~isPlainObject isPlainObject}
- */
-function isObject(x) {
-  return (
-    !isNullOrUndefined(x) &&
-    typeof x === 'object' &&
-    !Array.isArray(x) &&
-    Object.prototype.toString &&
-    /^\[object .+\]$/.test(Object.prototype.toString.call(x))
-  );
-}
-
-/**
- * Determines whether the provided value is a plain object (`{}`).
- *
- * This function returns `true` only if the value is a non-null object with
- * a prototype of `Object`.
- *
- * @param {any} x - The value to be checked.
- * @returns {boolean} `true` if the value is a plain object, otherwise `false`.
- *
- * @package
- * @since    1.1.0
- * @see      {@link module:utils~isObject isObject}
- */
-function isPlainObject(x) {
-  return (
-    !isNullOrUndefined(x) &&
-    typeof x === 'object' &&
-    !Array.isArray(x) &&
-    Object.prototype.toString &&
-    /^\[object Object\]$/.test(Object.prototype.toString.call(x))
-  );
-}
-
-/**
- * Returns the type of the provided value as a string.
- *
- * For `null` values, it returns `'null'`, and for objects, it returns a more detailed
- * type such as `'[object Object]'`.
- *
- * @param {any} x - The value whose type is to be determined.
- * @returns {string} A string representing the type of the value.
- *
- * @package
- * @since    1.1.0
- */
-function getType(x) {
-  return x === null
-    ? 'null' : typeof x === 'object'
-      ? Object.prototype.toString.call(x) : typeof x;
-}
-
-/**
- * **Logger Namespace**
- * @namespace module:utils~Logger
- * @public
- * @since  1.0.0
- */
-
-/**
- * A custom logger object for the **YTMP3** project with ANSI color codes.
- *
- * The logger is using the ANSI color codes to add color to the log messages,
- * it might not support on every terminals.
- *
- * @constant
- * @type {module:utils~Logger}
- * @public
- * @since  1.0.0
- * @see    {@link module:utils~Logger Logger (namespace)}
- * @see    {@link module:utils~LoggerInterface LoggerInterface}
- */
-const logger = Object.create(null);
-Object.defineProperties(logger, {
-  /**
-   * The prefix for the info level message.
-   * @memberof module:utils~Logger
-   * @var {string}
-   * @default <pre class=str>'\x1b[96m[INFO]\x1b[0m'</pre>
-   */
-  INFO_PREFIX: { value: '\x1b[96m[INFO]\x1b[0m', ...FrozenProperty },
-  /**
-   * The prefix for the done level message.
-   * @memberof module:utils~Logger
-   * @var {string}
-   * @default <pre class=str>'\x1b[92m[DONE]\x1b[0m'</pre>
-   */
-  DONE_PREFIX: { value: '\x1b[92m[DONE]\x1b[0m', ...FrozenProperty },
-  /**
-   * The prefix for the debug level message.
-   * @memberof module:utils~Logger
-   * @var {string}
-   * @default <pre class=str>'\x1b[2;37m[DEBUG]\x1b[0m'</pre>
-   */
-  DEBUG_PREFIX: { value: '\x1b[2;37m[DEBUG]\x1b[0m', ...FrozenProperty },
-  /**
-   * The prefix for the warning level message.
-   * @memberof module:utils~Logger
-   * @var {string}
-   * @default <pre class=str>'\x1b[93m[WARNING]\x1b[0m'</pre>
-   */
-  WARNING_PREFIX: { value: '\x1b[93m[WARNING]\x1b[0m', ...FrozenProperty },
-  /**
-   * The prefix for the error level message.
-   * @memberof module:utils~Logger
-   * @var {string}
-   * @default <pre class=str>'\x1b[91m[ERROR]\x1b[0m'</pre>
-   */
-  ERROR_PREFIX: { value: '\x1b[91m[ERROR]\x1b[0m', ...FrozenProperty },
-  /**
-   * The function to log the info level message to the console.
-   * @memberof module:utils~Logger
-   * @var {LoggerFunc}
-   * @function
-   */
-  info: {
-    value: function (msg) {
-      console.log(`${this.INFO_PREFIX} ${msg}`);
-    },
-    ...FrozenProperty
-  },
-  /**
-   * The function to log the done level message to the console.
-   * @memberof module:utils~Logger
-   * @function
-   * @param {string} msg - The message string to be displayed.
-   * @returns {void}
-   */
-  done: {
-    value: function (msg) {
-      console.log(`${this.DONE_PREFIX} ${msg}`);
-    },
-    ...FrozenProperty
-  },
-  /**
-   * The function to log the debug level message to the console.
-   * @memberof module:utils~Logger
-   * @function
-   * @param {string} msg - The message string to be displayed.
-   * @returns {void}
-   */
-  debug: {
-    value: function (msg) {
-      console.log(`${this.DEBUG_PREFIX} ${msg}`);
-    },
-    ...FrozenProperty
-  },
-  /**
-   * The function to log the warning level message to the console.
-   * @memberof module:utils~Logger
-   * @function
-   * @param {string} msg - The message string to be displayed.
-   * @returns {void}
-   */
-  warn: {
-    value: function (msg) {
-      console.error(`${this.WARNING_PREFIX} ${msg}`);
-    },
-    ...FrozenProperty
-  },
-  /**
-   * The function to log the error level message to the console.
-   * @memberof module:utils~Logger
-   * @function
-   * @param {string} msg - The message string to be displayed.
-   * @returns {void}
-   */
-  error: {
-    value: function (msg) {
-      console.error(`${this.ERROR_PREFIX} ${msg}`);
-    },
-    ...FrozenProperty
-  }
-});
-
-/**
- * Drops null and undefined values from the input object.
- *
- * @param {Object} obj - The input object to filter null and undefined values from.
- * @return {Object} The filtered object without null and undefined values.
- *
- * @public
- * @since  1.0.0
- */
-function dropNullAndUndefined(obj) {
-  return Object.keys(obj).reduce((acc, key) => {
-    if (!isNullOrUndefined(obj[key])) acc[key] = obj[key];
-    return acc;
-  }, {});
-}
-
-
 // region Utilities Class
 
 class ProgressBar {
@@ -388,12 +163,13 @@ class ProgressBar {
    * @class
    * @param {ProgressBarOptions} options
    *        Options object for configuring the progress bar.
+   * @package
    * @since 1.0.0
    */
   constructor (options) {
     /**
      * Options object for configuring the progress bar.
-     * @var {ResolvedProgressBarOptions}
+     * @type {ResolvedProgressBarOptions}
      */
     this.options = {
       barWidth: (typeof options?.barWidth === 'string'
@@ -411,12 +187,12 @@ class ProgressBar {
     };
     /**
      * Index for the loading animation.
-     * @var {number}
+     * @type {number}
      */
     this.idxLoading = 0;
     /**
      * Characters for the loading animation.
-     * @var {'\\' | '|' | '/' | '-'}
+     * @type {'\\' | '|' | '/' | '-'}
      * @default
      */
     this.loadings = [ '\\', '|', '/', '-' ];
@@ -497,17 +273,30 @@ class ProgressBar {
 }
 
 
-module.exports = Object.freeze({
+// Logger module
+Object.assign(module.exports, {
+  Logger,
+  log: Logger.log,
+  logger: Logger.logger
+});
+
+// TypeUtils module
+Object.assign(module.exports, {
+  TypeUtils,
+  ...TypeUtils
+});
+
+// URLUtils module
+Object.assign(module.exports, { URLUtils });
+
+// URLFmt module
+Object.assign(module.exports, { URLFmt });
+
+// Utils (this) module
+Object.assign(module.exports, {
   ROOTDIR, OUTDIR, LOGDIR, YTMP3_HOMEDIR,
-  logger,
-  log: logger, // alias for `logger`
-  isNullOrUndefined,
-  isObject,
-  isPlainObject,
   createDirIfNotExist,
   createDirIfNotExistSync,
   createLogFile,
-  dropNullAndUndefined,
-  getType,
   ProgressBar
 });
diff --git a/lib/utils/logger.js b/lib/utils/logger.js
new file mode 100644
index 0000000..2117cc9
--- /dev/null
+++ b/lib/utils/logger.js
@@ -0,0 +1,138 @@
+/**
+ * Utility submodule for logging process.
+ *
+ * @module    utils/logger
+ * @author    Ryuu Mitsuki <https://github.com/mitsuki31>
+ * @license   MIT
+ * @since     1.2.0
+ */
+
+'use strict';
+
+/**
+ * @classdesc A custom logger object for the **YTMP3-JS** library with ANSI color codes.
+ *
+ * The logger is using the ANSI color codes to add color to the log messages,
+ * it might not support on every terminals.
+ *
+ * @class
+ * @hideconstructor
+ * @package
+ * @since    1.0.0
+ */
+const Logger = {};
+
+/**
+ * The prefix for the info level message.
+ * @type    {string}
+ * @default <pre class=str>'\x1b[96m[INFO]\x1b[0m'</pre>
+ * @since   1.0.0
+ */
+Logger.INFO_PREFIX     = '\x1b[96m[INFO]\x1b[0m';
+
+/**
+ * The prefix for the done level message.
+ * @type    {string}
+ * @default <pre class=str>'\x1b[92m[DONE]\x1b[0m'</pre>
+ * @since   1.0.0
+ */
+Logger.DONE_PREFIX     = '\x1b[92m[DONE]\x1b[0m';
+
+/**
+ * The prefix for the debug level message.
+ * @type    {string}
+ * @default <pre class=str>'\x1b[2;37m[DEBUG]\x1b[0m'</pre>
+ * @since   1.0.0
+ */
+Logger.DEBUG_PREFIX    = '\x1b[2;37m[DEBUG]\x1b[0m';
+
+/**
+ * The prefix for the warning level message.
+ * @type    {string}
+ * @default <pre class=str>'\x1b[93m[WARNING]\x1b[0m'</pre>
+ * @since   1.0.0
+ */
+Logger.WARNING_PREFIX  = '\x1b[93m[WARNING]\x1b[0m';
+
+/**
+ * The prefix for the error level message.
+ * @type    {string}
+ * @default <pre class=str>'\x1b[91m[ERROR]\x1b[0m'</pre>
+ * @since   1.0.0
+ */
+Logger.ERROR_PREFIX    = '\x1b[91m[ERROR]\x1b[0m';
+
+/**
+ * The function to log the **info** level message to the console.
+ *
+ * @param     {string} [msg] - The message string to log.
+ *
+ * @function
+ * @package
+ * @since     1.0.0
+ */
+Logger.info = function info(msg) {
+  console.log(`${Logger.INFO_PREFIX} ${msg}`);
+};
+
+/**
+ * The function to log the **done** level message to the console.
+ *
+ * @param     {string} [msg] - The message string to log.
+ * @returns   {void}
+ *
+ * @function
+ * @package
+ * @since     1.0.0
+ */
+Logger.done = function done(msg) {
+  console.log(`${Logger.DONE_PREFIX} ${msg}`);
+};
+
+/**
+ * The function to log the **debug** level message to the console.
+ *
+ * @param     {string} [msg] - The message string to log.
+ * @returns   {void}
+ *
+ * @function
+ * @package
+ * @since     1.0.0
+ */
+Logger.debug = function debug(msg) {
+  console.log(`${Logger.DEBUG_PREFIX} ${msg}`);
+};
+
+/**
+ * The function to log the **warning** level message to the console.
+ *
+ * @param     {string} [msg] - The message string to log.
+ * @returns   {void}
+ *
+ * @function
+ * @package
+ * @since     1.0.0
+ */
+Logger.warn = function warn(msg) {
+  console.error(`${this.WARNING_PREFIX} ${msg}`);
+};
+
+/**
+ * The function to log the **error** level message to the console.
+ *
+ * @param     {string} [msg] - The message string to log.
+ * @returns   {void}
+ *
+ * @function
+ * @package
+ * @since     1.0.0
+ */
+Logger.error = function error(msg) {
+  console.error(`${this.ERROR_PREFIX} ${msg}`);
+};
+
+Logger.log = Logger;     // Circular reference #1 (new alias)
+Logger.logger = Logger;  // Circular reference #2 (for backward compatibility)
+
+// Export the `Logger` object with the circular references
+module.exports = Logger;
diff --git a/lib/utils/type-utils.js b/lib/utils/type-utils.js
new file mode 100644
index 0000000..306642c
--- /dev/null
+++ b/lib/utils/type-utils.js
@@ -0,0 +1,112 @@
+/**
+ * Utility submodule containing type checker and helper.
+ *
+ * @module    utils/type-utils
+ * @author    Ryuu Mitsuki <https://github.com/mitsuki31>
+ * @license   MIT
+ * @since     1.2.0
+ */
+
+'use strict';
+
+const TypeUtils = {};
+
+/**
+ * Checks if a given value is null or undefined.
+ *
+ * @param {any} x - The value to check.
+ * @returns {boolean} `true` if the value is null or undefined, otherwise `false`.
+ *
+ * @package
+ * @since  1.0.0
+ */
+function isNullOrUndefined(x) {
+  return (x === null || typeof x === 'undefined');
+}
+TypeUtils.isNullOrUndefined = isNullOrUndefined;  // Assign to `TypeUtils`
+
+/**
+ * Determines whether the provided value is a non-null object.
+ *
+ * This function returns `true` for any value that is of the object type and is not `null`, 
+ * but it does not guarantee that the object is a plain object (`{}`).
+ *
+ * @param {any} x - The value to be checked.
+ * @returns {boolean} `true` if the value is a non-null object, otherwise `false`.
+ *
+ * @package
+ * @since    1.0.0
+ * @see      {@link module:utils~isPlainObject isPlainObject}
+ */
+function isObject(x) {
+  return (
+    !isNullOrUndefined(x) &&
+    typeof x === 'object' &&
+    !Array.isArray(x) &&
+    Object.prototype.toString &&
+    /^\[object .+\]$/.test(Object.prototype.toString.call(x))
+  );
+}
+TypeUtils.isObject = isObject;  // Assign to `TypeUtils`
+
+/**
+ * Determines whether the provided value is a plain object (`{}`).
+ *
+ * This function returns `true` only if the value is a non-null object with
+ * a prototype of `Object`.
+ *
+ * @param {any} x - The value to be checked.
+ * @returns {boolean} `true` if the value is a plain object, otherwise `false`.
+ *
+ * @package
+ * @since    1.1.0
+ * @see      {@link module:utils~isObject isObject}
+ */
+function isPlainObject(x) {
+  return (
+    !isNullOrUndefined(x) &&
+    typeof x === 'object' &&
+    !Array.isArray(x) &&
+    Object.prototype.toString &&
+    /^\[object Object\]$/.test(Object.prototype.toString.call(x))
+  );
+}
+TypeUtils.isPlainObject = isPlainObject;  // Assign to `TypeUtils`
+
+/**
+ * Returns the type of the provided value as a string.
+ *
+ * For `null` values, it returns `'null'`, and for objects, it returns a more detailed
+ * type such as `'[object Object]'`.
+ *
+ * @param {any} x - The value whose type is to be determined.
+ * @returns {string} A string representing the type of the value.
+ *
+ * @package
+ * @since    1.1.0
+ */
+function getType(x) {
+  return x === null
+    ? 'null' : typeof x === 'object'
+      ? Object.prototype.toString.call(x) : typeof x;
+}
+TypeUtils.getType = getType;  // Assign to `TypeUtils`
+
+/**
+ * Drops null and undefined values from the input object.
+ *
+ * @param {Object} obj - The input object to filter null and undefined values from.
+ * @return {Object} The filtered object without null and undefined values.
+ *
+ * @package
+ * @since  1.0.0
+ */
+function dropNullAndUndefined(obj) {
+  return Object.keys(obj).reduce((acc, key) => {
+    if (!isNullOrUndefined(obj[key])) acc[key] = obj[key];
+    return acc;
+  }, {});
+}
+TypeUtils.dropNullAndUndefined = dropNullAndUndefined;  // Assign to `TypeUtils`
+
+module.exports = TypeUtils;
diff --git a/lib/url-utils.js b/lib/utils/url-utils.js
similarity index 96%
rename from lib/url-utils.js
rename to lib/utils/url-utils.js
index eeb5900..2034c51 100644
--- a/lib/url-utils.js
+++ b/lib/utils/url-utils.js
@@ -1,17 +1,16 @@
 /**
- * A module provides utilities for working with YouTube URLs.
+ * A submodule provides utilities for working with YouTube URLs.
  *
- * @module    url-utils
- * @requires  utils
- * @author    Ryuu Mitsuki (https://github.com/mitsuki31)
+ * @module    utils/url-utils
+ * @author    Ryuu Mitsuki <https://github.com/mitsuki31>
  * @license   MIT
  * @since     1.1.0
  */
 
 'use strict';
 
-const { isNullOrUndefined } = require('./utils');
-const { IDExtractorError } = require('./error');
+const { isNullOrUndefined } = require('./type-utils');
+const { IDExtractorError } = require('../error');
 
 
 /**
diff --git a/lib/yt-urlfmt.js b/lib/utils/yt-urlfmt.js
similarity index 97%
rename from lib/yt-urlfmt.js
rename to lib/utils/yt-urlfmt.js
index 6f6fd93..f67cb49 100644
--- a/lib/yt-urlfmt.js
+++ b/lib/utils/yt-urlfmt.js
@@ -16,8 +16,8 @@
  * This allows the library to handle a broader range of YouTube-related URLs
  * effectively.
  *
- * @module   yt-urlfmt
- * @author   Ryuu Mitsuki (https://github.com/mitsuki31)
+ * @module   utils/yt-urlfmt
+ * @author   Ryuu Mitsuki <https://github.com/mitsuki31>
  * @license  MIT
  * @since    1.0.0
  */
diff --git a/lib/ytmp3.js b/lib/ytmp3.js
index db266ce..93a9456 100644
--- a/lib/ytmp3.js
+++ b/lib/ytmp3.js
@@ -33,8 +33,7 @@
  * @version   1.1.0
  * @requires  audioconv
  * @requires  utils
- * @requires  url-utils
- * @author    Ryuu Mitsuki (https://github.com/mitsuki31)
+ * @author    Ryuu Mitsuki <https://github.com/mitsuki31>
  * @license   MIT
  * @since     1.0.0
  */
@@ -55,6 +54,7 @@ const {
   LOGDIR,
   logger: log,
   ProgressBar,
+  URLUtils,
   createDirIfNotExist,
   createDirIfNotExistSync,
   createLogFile
@@ -64,7 +64,6 @@ const {
   convertAudio,
   defaultOptions: defaultAudioConvOptions
 } = require('./audioconv');
-const URLUtils = require('./url-utils');
 
 /**
  * The video information object.
diff --git a/test/irl.test.mjs b/test/irl.test.mjs
index 30d2c51..cc88f6c 100644
--- a/test/irl.test.mjs
+++ b/test/irl.test.mjs
@@ -13,7 +13,7 @@ import ffmpeg from 'fluent-ffmpeg';
 
 import audioconv from '../lib/audioconv.js';
 import ytmp3 from '../lib/ytmp3.js';
-import utils from '../lib/utils.js';
+import utils from '../lib/utils/index.js';
 
 const ffprobe = promisify(ffmpeg.ffprobe);
 const createTempPath = promisify(_createTempPath);
diff --git a/test/unittest/audioconv.spec.mjs b/test/unittest/audioconv.spec.mjs
index b6cb56e..88fbba0 100644
--- a/test/unittest/audioconv.spec.mjs
+++ b/test/unittest/audioconv.spec.mjs
@@ -5,7 +5,7 @@ import childProcess from 'node:child_process';
 import { getTempPath } from '@mitsuki31/temppath';
 
 import audioconv from '../../lib/audioconv.js';
-import utils from '../../lib/utils.js';
+import utils from '../../lib/utils/index.js';
 
 describe('module:audioconv', function () {
   const testMessages = {
diff --git a/test/unittest/config.spec.mjs b/test/unittest/config.spec.mjs
index f13e2bf..8685b92 100644
--- a/test/unittest/config.spec.mjs
+++ b/test/unittest/config.spec.mjs
@@ -8,7 +8,7 @@ import { lsFiles } from 'lsfnd';
 import { getTempPath } from '@mitsuki31/temppath';
 
 import config from '../../lib/config.js';
-import utils from'../../lib/utils.js';
+import utils from '../../lib/utils/index.js';
 import audioconv from '../../lib/audioconv.js';
 import error from '../../lib/error.js';
 const {
diff --git a/test/unittest/url-utils.spec.mjs b/test/unittest/url-utils.spec.mjs
index cac11ba..7d26be0 100644
--- a/test/unittest/url-utils.spec.mjs
+++ b/test/unittest/url-utils.spec.mjs
@@ -1,6 +1,6 @@
 import assert from 'node:assert';
 
-import URLUtils from '../../lib/url-utils.js';
+import URLUtils from '../../lib/utils/url-utils.js';
 import error from '../../lib/error.js';
 const { IDExtractorError } = error;
 
diff --git a/test/unittest/utils.spec.mjs b/test/unittest/utils.spec.mjs
index ac47e0f..01c1b33 100644
--- a/test/unittest/utils.spec.mjs
+++ b/test/unittest/utils.spec.mjs
@@ -4,7 +4,7 @@ import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { getTempPath } from '@mitsuki31/temppath';
 
-import utils from '../../lib/utils.js';
+import utils from '../../lib/utils/index.js';
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
diff --git a/test/unittest/yt-urlfmt.spec.mjs b/test/unittest/yt-urlfmt.spec.mjs
index 79b5dd6..11437bf 100644
--- a/test/unittest/yt-urlfmt.spec.mjs
+++ b/test/unittest/yt-urlfmt.spec.mjs
@@ -1,6 +1,6 @@
 import assert from 'node:assert';
 
-import yturlfmt from '../../lib/yt-urlfmt.js';
+import yturlfmt from '../../lib/utils/yt-urlfmt.js';
 
 describe('module:yt-urlfmt', function () {
   const testMessage = 'check and validate regular expression';
diff --git a/test/unittest/ytmp3.spec.mjs b/test/unittest/ytmp3.spec.mjs
index d2939db..cf5537b 100644
--- a/test/unittest/ytmp3.spec.mjs
+++ b/test/unittest/ytmp3.spec.mjs
@@ -5,7 +5,7 @@ import { getTempPath } from '@mitsuki31/temppath';
 
 import ytmp3 from '../../lib/ytmp3.js';
 import audioconv from '../../lib/audioconv.js';
-import utils from '../../lib/utils.js';
+import utils from '../../lib/utils/index.js';
 const pkg = JSON.parse(
   fs.readFileSync(path.join(utils.ROOTDIR, 'package.json'), 'utf8'));