diff --git a/composer.json b/composer.json
index 2cca38d..9188bc2 100644
--- a/composer.json
+++ b/composer.json
@@ -21,6 +21,7 @@
     ],
     "require" : {
         "ext-dom": "*",
+        "ext-mbstring": "*",
         "php" : ">=7.4"
     },
     "require-dev": {
diff --git a/src/HTML5/Parser/UTF8Utils.php b/src/HTML5/Parser/UTF8Utils.php
index 4405e4c..eb1071f 100644
--- a/src/HTML5/Parser/UTF8Utils.php
+++ b/src/HTML5/Parser/UTF8Utils.php
@@ -27,7 +27,6 @@
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-use Masterminds\HTML5\Exception;
 
 class UTF8Utils
 {
@@ -38,7 +37,7 @@ class UTF8Utils
 
     /**
      * Count the number of characters in a string.
-     * UTF-8 aware. This will try (in order) iconv, MB, and finally a custom counter.
+     * UTF-8 aware.
      *
      * @param string $string
      *
@@ -46,20 +45,7 @@ class UTF8Utils
      */
     public static function countChars($string)
     {
-        // Get the length for the string we need.
-        if (function_exists('mb_strlen')) {
-            return mb_strlen($string, 'utf-8');
-        }
-
-        if (function_exists('iconv_strlen')) {
-            return iconv_strlen($string, 'utf-8');
-        }
-
-        $count = count_chars($string);
-
-        // 0x80 = 0x7F - 0 + 1 (one added to get inclusive range)
-        // 0x33 = 0xF4 - 0x2C + 1 (one added to get inclusive range)
-        return array_sum(array_slice($count, 0, 0x80)) + array_sum(array_slice($count, 0xC2, 0x33));
+        return mb_strlen($string, 'utf-8');
     }
 
     /**
@@ -88,32 +74,20 @@ public static function convertToUTF8($data, $encoding = 'UTF-8')
         // details for the bug are on http://us1.php.net/manual/en/function.iconv.php#108643
         // which contains links to the actual but reports as well as work around
         // details.
-        if (function_exists('mb_convert_encoding')) {
-            // mb library has the following behaviors:
-            // - UTF-16 surrogates result in false.
-            // - Overlongs and outside Plane 16 result in empty strings.
-
-            // Before we run mb_convert_encoding we need to tell it what to do with
-            // characters it does not know. This could be different than the parent
-            // application executing this library so we store the value, change it
-            // to our needs, and then change it back when we are done. This feels
-            // a little excessive and it would be great if there was a better way.
-            $save = mb_substitute_character();
-            mb_substitute_character('none');
-            $data = mb_convert_encoding($data, 'UTF-8', $encoding);
-            mb_substitute_character($save);
-        }
-        // @todo Get iconv running in at least some environments if that is possible.
-        elseif (function_exists('iconv') && 'auto' !== $encoding) {
-            // fprintf(STDOUT, "iconv found\n");
-            // iconv has the following behaviors:
-            // - Overlong representations are ignored.
-            // - Beyond Plane 16 is replaced with a lower char.
-            // - Incomplete sequences generate a warning.
-            $data = @iconv($encoding, 'UTF-8//IGNORE', $data);
-        } else {
-            throw new Exception('Not implemented, please install mbstring or iconv');
-        }
+        //
+        // mb library has the following behaviors:
+        // - UTF-16 surrogates result in false.
+        // - Overlongs and outside Plane 16 result in empty strings.
+
+        // Before we run mb_convert_encoding we need to tell it what to do with
+        // characters it does not know. This could be different than the parent
+        // application executing this library so we store the value, change it
+        // to our needs, and then change it back when we are done. This feels
+        // a little excessive and it would be great if there was a better way.
+        $save = mb_substitute_character();
+        mb_substitute_character('none');
+        $data = mb_convert_encoding($data, 'UTF-8', $encoding);
+        mb_substitute_character($save);
 
         /*
          * One leading U+FEFF BYTE ORDER MARK character must be ignored if any are present.