diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0b81bfd..b1a63b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,17 +1,23 @@
 # Changelog
 
-### 0.14.x
-#### 0.14.1: Patch changelog
+## 0.15.0: Preview Image Resizing Update
+- Added the ability to change the preview image size dynamically.
+- Previously, the image was processed and displayed at its original size, causing lag or unresponsiveness when adjusting the slider.
+- Reducing the processed image size should help improve performance.
+- Default preview image size is now **25%**, but users can adjust it between **10% and 100%**.
+
+## 0.14.x
+### 0.14.1: Patch changelog
 - Updated the changelog to include missing entries.
 
-#### 0.14.0: Code refactor (by Mr. Finch)
+### 0.14.0: Code refactor (by Mr. Finch)
 - Introduced constants and optimized the code.
 
-### 0.13.x
-#### 0.13.1: Fixed image processing
+## 0.13.x
+### 0.13.1: Fixed image processing
 - Fixed a bug that made it impossible to process images.
 
-#### 0.13.0: Requirements file (by Mr. Finch)
+### 0.13.0: Requirements file (by Mr. Finch)
 - Added a requirements file.
 
 ## 0.12.x
diff --git a/src/OptimaLab35/gui.py b/src/OptimaLab35/gui.py
index 35d8707..187a8c1 100644
--- a/src/OptimaLab35/gui.py
+++ b/src/OptimaLab35/gui.py
@@ -858,12 +858,13 @@ class PreviewWindow(QMainWindow, Ui_Preview_Window):
         path = self.ui.image_path_lineEdit.text()
 
         worker = ImageProcessorWorker(
-            path=path,
-            optima_manager=self.o,
-            brightness=int(self.ui.brightness_spinBox.text()),
-            contrast=int(self.ui.contrast_spinBox.text()),
-            grayscale=self.ui.grayscale_checkBox.isChecked(),
-            callback=self.display_image  # Callback to update UI
+            path = path,
+            optima_manager = self.o,
+            brightness = int(self.ui.brightness_spinBox.text()),
+            contrast = int(self.ui.contrast_spinBox.text()),
+            grayscale = self.ui.grayscale_checkBox.isChecked(),
+            resize = self.ui.scale_Slider.value(),
+            callback = self.display_image  # Callback to update UI
         )
         self.threadpool.start(worker)  # Run worker in a thread
 
@@ -943,13 +944,14 @@ class ImageProcessorRunnable(QRunnable):
 class ImageProcessorWorker(QRunnable):
     """Worker class to load and process the image in a separate thread."""
     # ChatGPT
-    def __init__(self, path, optima_manager, brightness, contrast, grayscale, callback):
+    def __init__(self, path, optima_manager, brightness, contrast, grayscale, resize, callback):
         super().__init__()
         self.path = path
         self.optima_manager = optima_manager
         self.brightness = brightness
         self.contrast = contrast
         self.grayscale = grayscale
+        self.resize = resize
         self.callback = callback  # Function to call when processing is done
 
     @Slot()
@@ -961,12 +963,12 @@ class ImageProcessorWorker(QRunnable):
 
         try:
             img = self.optima_manager.process_image_object(
-                image_input_file=self.path,
-                watermark="PREVIEW",
-                resize=100,
-                grayscale=self.grayscale,
-                brightness=self.brightness,
-                contrast=self.contrast
+                image_input_file = self.path,
+                watermark = "PREVIEW",
+                resize = self.resize,
+                grayscale = self.grayscale,
+                brightness = self.brightness,
+                contrast = self.contrast
             )
             pixmap = QPixmap.fromImage(img)
             self.callback(pixmap)
diff --git a/src/OptimaLab35/ui/preview_window.py b/src/OptimaLab35/ui/preview_window.py
index 3381324..b210144 100644
--- a/src/OptimaLab35/ui/preview_window.py
+++ b/src/OptimaLab35/ui/preview_window.py
@@ -43,8 +43,8 @@ class Ui_Preview_Window(object):
         self.widget.setObjectName(u"widget")
         self.widget.setMinimumSize(QSize(160, 628))
         self.widget.setMaximumSize(QSize(150, 16777215))
-        self.verticalLayout_5 = QVBoxLayout(self.widget)
-        self.verticalLayout_5.setObjectName(u"verticalLayout_5")
+        self.verticalLayout_4 = QVBoxLayout(self.widget)
+        self.verticalLayout_4.setObjectName(u"verticalLayout_4")
         self.groupBox_3 = QGroupBox(self.widget)
         self.groupBox_3.setObjectName(u"groupBox_3")
         self.verticalLayout_3 = QVBoxLayout(self.groupBox_3)
@@ -60,7 +60,7 @@ class Ui_Preview_Window(object):
         self.verticalLayout_3.addWidget(self.load_Button)
 
 
-        self.verticalLayout_5.addWidget(self.groupBox_3)
+        self.verticalLayout_4.addWidget(self.groupBox_3)
 
         self.groupBox_2 = QGroupBox(self.widget)
         self.groupBox_2.setObjectName(u"groupBox_2")
@@ -87,7 +87,7 @@ class Ui_Preview_Window(object):
         self.verticalLayout.addWidget(self.reset_brightness_Button)
 
 
-        self.verticalLayout_5.addWidget(self.groupBox_2)
+        self.verticalLayout_4.addWidget(self.groupBox_2)
 
         self.groupBox = QGroupBox(self.widget)
         self.groupBox.setObjectName(u"groupBox")
@@ -114,7 +114,7 @@ class Ui_Preview_Window(object):
         self.verticalLayout_2.addWidget(self.reset_contrast_Button)
 
 
-        self.verticalLayout_5.addWidget(self.groupBox)
+        self.verticalLayout_4.addWidget(self.groupBox)
 
         self.groupBox_5 = QGroupBox(self.widget)
         self.groupBox_5.setObjectName(u"groupBox_5")
@@ -126,43 +126,58 @@ class Ui_Preview_Window(object):
         self.gridLayout.addWidget(self.grayscale_checkBox, 0, 0, 1, 1)
 
 
-        self.verticalLayout_5.addWidget(self.groupBox_5)
+        self.verticalLayout_4.addWidget(self.groupBox_5)
 
         self.verticalSpacer = QSpacerItem(20, 219, QSizePolicy.Policy.Minimum, QSizePolicy.Policy.Expanding)
 
-        self.verticalLayout_5.addItem(self.verticalSpacer)
+        self.verticalLayout_4.addItem(self.verticalSpacer)
 
         self.groupBox_4 = QGroupBox(self.widget)
         self.groupBox_4.setObjectName(u"groupBox_4")
-        self.verticalLayout_4 = QVBoxLayout(self.groupBox_4)
-        self.verticalLayout_4.setObjectName(u"verticalLayout_4")
+        self.gridLayout_2 = QGridLayout(self.groupBox_4)
+        self.gridLayout_2.setObjectName(u"gridLayout_2")
         self.live_update = QCheckBox(self.groupBox_4)
         self.live_update.setObjectName(u"live_update")
         self.live_update.setChecked(True)
 
-        self.verticalLayout_4.addWidget(self.live_update)
+        self.gridLayout_2.addWidget(self.live_update, 0, 0, 1, 1)
+
+        self.scale_label = QLabel(self.groupBox_4)
+        self.scale_label.setObjectName(u"scale_label")
+
+        self.gridLayout_2.addWidget(self.scale_label, 0, 1, 1, 1)
+
+        self.scale_Slider = QSlider(self.groupBox_4)
+        self.scale_Slider.setObjectName(u"scale_Slider")
+        self.scale_Slider.setMinimum(10)
+        self.scale_Slider.setMaximum(100)
+        self.scale_Slider.setPageStep(10)
+        self.scale_Slider.setValue(25)
+        self.scale_Slider.setOrientation(Qt.Horizontal)
+
+        self.gridLayout_2.addWidget(self.scale_Slider, 1, 0, 1, 2)
 
         self.update_Button = QPushButton(self.groupBox_4)
         self.update_Button.setObjectName(u"update_Button")
         self.update_Button.setEnabled(False)
         self.update_Button.setAutoFillBackground(False)
 
-        self.verticalLayout_4.addWidget(self.update_Button)
+        self.gridLayout_2.addWidget(self.update_Button, 2, 0, 1, 2)
 
         self.checkBox = QCheckBox(self.groupBox_4)
         self.checkBox.setObjectName(u"checkBox")
         self.checkBox.setLayoutDirection(Qt.LeftToRight)
         self.checkBox.setChecked(True)
 
-        self.verticalLayout_4.addWidget(self.checkBox)
+        self.gridLayout_2.addWidget(self.checkBox, 3, 0, 1, 2)
 
         self.close_Button = QPushButton(self.groupBox_4)
         self.close_Button.setObjectName(u"close_Button")
 
-        self.verticalLayout_4.addWidget(self.close_Button)
+        self.gridLayout_2.addWidget(self.close_Button, 4, 0, 1, 2)
 
 
-        self.verticalLayout_5.addWidget(self.groupBox_4)
+        self.verticalLayout_4.addWidget(self.groupBox_4)
 
 
         self.horizontalLayout.addWidget(self.widget)
@@ -170,7 +185,7 @@ class Ui_Preview_Window(object):
         Preview_Window.setCentralWidget(self.centralwidget)
         self.menubar = QMenuBar(Preview_Window)
         self.menubar.setObjectName(u"menubar")
-        self.menubar.setGeometry(QRect(0, 0, 875, 27))
+        self.menubar.setGeometry(QRect(0, 0, 875, 22))
         Preview_Window.setMenuBar(self.menubar)
 
         self.retranslateUi(Preview_Window)
@@ -179,6 +194,7 @@ class Ui_Preview_Window(object):
         self.contrast_Slider.valueChanged.connect(self.contrast_spinBox.setValue)
         self.contrast_spinBox.valueChanged.connect(self.contrast_Slider.setValue)
         self.live_update.toggled.connect(self.update_Button.setDisabled)
+        self.scale_Slider.valueChanged.connect(self.scale_label.setNum)
 
         QMetaObject.connectSlotsByName(Preview_Window)
     # setupUi
@@ -212,6 +228,13 @@ class Ui_Preview_Window(object):
         self.live_update.setToolTip(QCoreApplication.translate("Preview_Window", u"Live update applies changes instantly. If the app becomes unresponsive or lags, disable this option.", None))
 #endif // QT_CONFIG(tooltip)
         self.live_update.setText(QCoreApplication.translate("Preview_Window", u"Live refresh", None))
+#if QT_CONFIG(tooltip)
+        self.scale_label.setToolTip(QCoreApplication.translate("Preview_Window", u"Sets the resize value for the preview image. A high value may cause the application to freeze.", None))
+#endif // QT_CONFIG(tooltip)
+        self.scale_label.setText(QCoreApplication.translate("Preview_Window", u"25", None))
+#if QT_CONFIG(tooltip)
+        self.scale_Slider.setToolTip(QCoreApplication.translate("Preview_Window", u"Sets the resize value for the preview image. A high value may cause the application to freeze.", None))
+#endif // QT_CONFIG(tooltip)
 #if QT_CONFIG(tooltip)
         self.update_Button.setToolTip(QCoreApplication.translate("Preview_Window", u"Apply Changes to Preview", None))
 #endif // QT_CONFIG(tooltip)
diff --git a/src/OptimaLab35/ui/preview_window.ui b/src/OptimaLab35/ui/preview_window.ui
index 1e8066f..3408bd7 100644
--- a/src/OptimaLab35/ui/preview_window.ui
+++ b/src/OptimaLab35/ui/preview_window.ui
@@ -54,7 +54,7 @@
         <height>16777215</height>
        </size>
       </property>
-      <layout class="QVBoxLayout" name="verticalLayout_5">
+      <layout class="QVBoxLayout" name="verticalLayout_4">
        <item>
         <widget class="QGroupBox" name="groupBox_3">
          <property name="title">
@@ -202,8 +202,8 @@
          <property name="title">
           <string>Behavior</string>
          </property>
-         <layout class="QVBoxLayout" name="verticalLayout_4">
-          <item>
+         <layout class="QGridLayout" name="gridLayout_2">
+          <item row="0" column="0">
            <widget class="QCheckBox" name="live_update">
             <property name="toolTip">
              <string>Live update applies changes instantly. If the app becomes unresponsive or lags, disable this option.</string>
@@ -216,7 +216,39 @@
             </property>
            </widget>
           </item>
-          <item>
+          <item row="0" column="1">
+           <widget class="QLabel" name="scale_label">
+            <property name="toolTip">
+             <string>Sets the resize value for the preview image. A high value may cause the application to freeze.</string>
+            </property>
+            <property name="text">
+             <string>25</string>
+            </property>
+           </widget>
+          </item>
+          <item row="1" column="0" colspan="2">
+           <widget class="QSlider" name="scale_Slider">
+            <property name="toolTip">
+             <string>Sets the resize value for the preview image. A high value may cause the application to freeze.</string>
+            </property>
+            <property name="minimum">
+             <number>10</number>
+            </property>
+            <property name="maximum">
+             <number>100</number>
+            </property>
+            <property name="pageStep">
+             <number>10</number>
+            </property>
+            <property name="value">
+             <number>25</number>
+            </property>
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+           </widget>
+          </item>
+          <item row="2" column="0" colspan="2">
            <widget class="QPushButton" name="update_Button">
             <property name="enabled">
              <bool>false</bool>
@@ -232,7 +264,7 @@
             </property>
            </widget>
           </item>
-          <item>
+          <item row="3" column="0" colspan="2">
            <widget class="QCheckBox" name="checkBox">
             <property name="toolTip">
              <string>Enable to copy adjustments to the main window upon closing</string>
@@ -248,7 +280,7 @@
             </property>
            </widget>
           </item>
-          <item>
+          <item row="4" column="0" colspan="2">
            <widget class="QPushButton" name="close_Button">
             <property name="toolTip">
              <string/>
@@ -272,7 +304,7 @@
      <x>0</x>
      <y>0</y>
      <width>875</width>
-     <height>27</height>
+     <height>22</height>
     </rect>
    </property>
   </widget>
@@ -359,5 +391,21 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>scale_Slider</sender>
+   <signal>valueChanged(int)</signal>
+   <receiver>scale_label</receiver>
+   <slot>setNum(int)</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>783</x>
+     <y>644</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>831</x>
+     <y>619</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
 </ui>