diff --git a/BifcodePackage/Sources/BifcodeFeature/ContentView.swift b/BifcodePackage/Sources/BifcodeFeature/ContentView.swift
index 24e6a78..8e1ad65 100644
--- a/BifcodePackage/Sources/BifcodeFeature/ContentView.swift
+++ b/BifcodePackage/Sources/BifcodeFeature/ContentView.swift
@@ -91,6 +91,9 @@ public struct ContentView: View {
     @AppStorage("fontSize") private var fontSize: Double = 14
     @AppStorage("selectedTheme") private var selectedThemeRaw: String = EditorThemeOption.atomOneDark.rawValue
     @AppStorage("themeMode") private var themeModeRaw: String = ThemeMode.dark.rawValue
+    @AppStorage("useCustomDimensions") private var useCustomDimensions: Bool = false
+    @AppStorage("customExportWidth") private var customExportWidth: Double = 1200
+    @AppStorage("customExportHeight") private var customExportHeight: Double = 675
     
     private var layout: WindowLayout {
         WindowLayout(rawValue: windowLayoutRaw) ?? .horizontal
@@ -445,8 +448,60 @@ public struct ContentView: View {
         let finalImage = NSImage(size: size)
         finalImage.addRepresentation(scaledBitmapRep)
         
+        // Apply custom dimensions scaling if enabled
+        if useCustomDimensions {
+            let targetSize = CGSize(width: customExportWidth, height: customExportHeight)
+            return scaleImageToCustomSize(finalImage, targetSize: targetSize)
+        }
+        
         return finalImage
     }
+    
+    /// Scales an image to fit within the target custom size while maintaining aspect ratio.
+    ///
+    /// The image is scaled to fit within the custom dimensions, centered on a transparent background.
+    /// Content is scaled down if larger than target, or centered without scaling if smaller.
+    ///
+    /// - Parameters:
+    ///   - image: The source image to scale.
+    ///   - targetSize: The target dimensions from custom export settings.
+    /// - Returns: A new image at the exact custom dimensions.
+    @MainActor
+    private func scaleImageToCustomSize(_ image: NSImage, targetSize: CGSize) -> NSImage {
+        let sourceSize = image.size
+        
+        // Calculate scale to fit within target while maintaining aspect ratio
+        let widthRatio = targetSize.width / sourceSize.width
+        let heightRatio = targetSize.height / sourceSize.height
+        let scale = min(widthRatio, heightRatio, 1.0) // Don't scale up, only down
+        
+        let scaledWidth = sourceSize.width * scale
+        let scaledHeight = sourceSize.height * scale
+        
+        // Center the scaled content within the target size
+        let xOffset = (targetSize.width - scaledWidth) / 2
+        let yOffset = (targetSize.height - scaledHeight) / 2
+        
+        // Create the final image at custom dimensions
+        let customImage = NSImage(size: targetSize)
+        customImage.lockFocus()
+        
+        // Clear background (transparent)
+        NSColor.clear.setFill()
+        NSRect(origin: .zero, size: targetSize).fill()
+        
+        // Draw the scaled image centered
+        image.draw(
+            in: NSRect(x: xOffset, y: yOffset, width: scaledWidth, height: scaledHeight),
+            from: .zero,
+            operation: .copy,
+            fraction: 1.0
+        )
+        
+        customImage.unlockFocus()
+        
+        return customImage
+    }
 }
 
 // MARK: - Preview
diff --git a/BifcodePackage/Sources/BifcodeFeature/Views/ToolBarView.swift b/BifcodePackage/Sources/BifcodeFeature/Views/ToolBarView.swift
index 1232ac2..976e090 100644
--- a/BifcodePackage/Sources/BifcodeFeature/Views/ToolBarView.swift
+++ b/BifcodePackage/Sources/BifcodeFeature/Views/ToolBarView.swift
@@ -60,6 +60,10 @@ public struct ToolBarView: View {
     @AppStorage("fontSize") private var fontSize: Double = 14
     @AppStorage("selectedTheme") private var selectedThemeRaw: String = EditorThemeOption.atomOneDark.rawValue
     @AppStorage("themeMode") private var themeModeRaw: String = ThemeMode.dark.rawValue
+    @AppStorage("useCustomDimensions") private var useCustomDimensions: Bool = false
+    @AppStorage("customExportWidth") private var customExportWidth: Double = 1200
+    @AppStorage("customExportHeight") private var customExportHeight: Double = 675
+    @AppStorage("lockAspectRatio") private var lockAspectRatio: Bool = true
     
     @AppStorage("selectedLanguage") private var selectedLanguageRaw: String = "swift"
     
@@ -544,6 +548,19 @@ public struct ToolBarView: View {
                 ? "Disabled: Add code to enable export"
                 : "Save comparison image to selected folder")
             
+            // Custom Dimensions Toggle
+            Toggle("Size", isOn: $useCustomDimensions)
+                .toggleStyle(.checkbox)
+                .font(.caption)
+                .help("Use custom export dimensions")
+                .accessibilityLabel("Custom Size")
+                .accessibilityHint(useCustomDimensions ? "Custom dimensions enabled" : "Auto-size based on content")
+            
+            // Custom Dimensions Fields
+            if useCustomDimensions {
+                customDimensionsFields
+            }
+            
             // Secondary Actions
             VStack(spacing: 8) {
                 Button {
@@ -558,10 +575,71 @@ public struct ToolBarView: View {
                 .accessibilityHint("Select folder for exported images")
                 
                 storeButton
-                    .padding(.top, 32)
+                    .padding(.top, useCustomDimensions ? 8 : 32)
+            }
+        }
+        .frame(minWidth: 120)
+    }
+    
+    /// Stores the aspect ratio when locking is enabled
+    @State private var lockedAspectRatio: Double = 1200.0 / 675.0
+    
+    private var customDimensionsFields: some View {
+        VStack(spacing: 6) {
+            // Width field
+            HStack(spacing: 4) {
+                Text("W")
+                    .font(.caption2)
+                    .foregroundStyle(Color.tertiaryText)
+                    .frame(width: 12)
+                TextField("Width", value: $customExportWidth, format: .number)
+                    .textFieldStyle(.roundedBorder)
+                    .frame(width: 60)
+                    .onChange(of: customExportWidth) { oldValue, newValue in
+                        if lockAspectRatio, oldValue != newValue {
+                            let clampedWidth = min(max(newValue, 100), 4096)
+                            customExportHeight = clampedWidth / lockedAspectRatio
+                        }
+                    }
+            }
+            .accessibilityElement(children: .combine)
+            .accessibilityLabel("Width")
+            .accessibilityValue("\(Int(customExportWidth)) pixels")
+            
+            // Height field
+            HStack(spacing: 4) {
+                Text("H")
+                    .font(.caption2)
+                    .foregroundStyle(Color.tertiaryText)
+                    .frame(width: 12)
+                TextField("Height", value: $customExportHeight, format: .number)
+                    .textFieldStyle(.roundedBorder)
+                    .frame(width: 60)
+                    .onChange(of: customExportHeight) { oldValue, newValue in
+                        if lockAspectRatio, oldValue != newValue {
+                            let clampedHeight = min(max(newValue, 100), 4096)
+                            customExportWidth = clampedHeight * lockedAspectRatio
+                        }
+                    }
+            }
+            .accessibilityElement(children: .combine)
+            .accessibilityLabel("Height")
+            .accessibilityValue("\(Int(customExportHeight)) pixels")
+            
+            // Aspect ratio lock
+            Button {
+                lockAspectRatio.toggle()
+                if lockAspectRatio {
+                    lockedAspectRatio = customExportWidth / max(customExportHeight, 1)
+                }
+            } label: {
+                Image(systemName: lockAspectRatio ? "lock.fill" : "lock.open")
+                    .font(.caption)
             }
+            .buttonStyle(.borderless)
+            .help(lockAspectRatio ? "Unlock aspect ratio" : "Lock aspect ratio")
+            .accessibilityLabel(lockAspectRatio ? "Aspect ratio locked" : "Aspect ratio unlocked")
         }
-        .frame(minWidth: 80)
     }
     
     private var storeButton: some View {