diff --git a/src/os/unix/x11.rs b/src/os/unix/x11.rs
index d20f693..f6d59f7 100644
--- a/src/os/unix/x11.rs
+++ b/src/os/unix/x11.rs
@@ -273,6 +273,7 @@ pub struct Window {
     scroll_y: f32,
     buttons: [u8; 3],
     prev_cursor: CursorStyle,
+    active: bool,
 
     should_close: bool, // received delete window message from X server
 
@@ -363,7 +364,8 @@ impl Window {
                     | xlib::KeyPressMask
                     | xlib::KeyReleaseMask
                     | xlib::ButtonPressMask
-                    | xlib::ButtonReleaseMask,
+                    | xlib::ButtonReleaseMask
+                    | xlib::FocusChangeMask,
             );
 
             if !opts.resize {
@@ -416,6 +418,7 @@ impl Window {
                 buttons: [0, 0, 0],
                 prev_cursor: CursorStyle::Arrow,
                 should_close: false,
+                active: false,
                 key_handler: KeyHandler::new(),
                 update_rate: UpdateRate::new(),
                 menu_counter: MenuHandle(0),
@@ -633,8 +636,7 @@ impl Window {
 
     #[inline]
     pub fn is_active(&mut self) -> bool {
-        // TODO: Proper implementation
-        true
+        self.active
     }
 
     fn get_scale_factor(
@@ -866,6 +868,12 @@ impl Window {
                 )
                 .expect("todo");
             }
+            xlib::FocusOut => {
+                self.active = false;
+            }
+            xlib::FocusIn => {
+                self.active = true;
+            }
 
             _ => {}
         }
diff --git a/src/os/windows/mod.rs b/src/os/windows/mod.rs
index 0c3ebc6..7dc260b 100644
--- a/src/os/windows/mod.rs
+++ b/src/os/windows/mod.rs
@@ -828,8 +828,17 @@ impl Window {
 
     #[inline]
     pub fn is_active(&mut self) -> bool {
-        // TODO: Proper implementation
-        true
+        match self.window {
+            Some(hwnd) => {
+                let active = unsafe { winapi::um::winuser::GetActiveWindow() };
+                if !active.is_null() && active == hwnd {
+                    true
+                } else {
+                    false
+                }
+            }
+            None => false,
+        }
     }
 
     unsafe fn get_scale_factor(width: usize, height: usize, scale: Scale) -> i32 {