diff --git a/Cargo.toml b/Cargo.toml
index 1139cb007..16341302c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -45,7 +45,7 @@ bevy = { version = "0.10", default-features = false, features = [
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 winit = "0.28"
-web-sys = { version = "*", features = [
+web-sys = { version = "0.3.63", features = [
     "Clipboard",
     "ClipboardEvent",
     "DataTransfer",
diff --git a/src/lib.rs b/src/lib.rs
index 1eb5f77a6..ef7a9bcb8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -144,10 +144,6 @@ impl Default for EguiSettings {
 #[derive(Component, Clone, Debug, Default, Deref, DerefMut)]
 pub struct EguiInput(pub egui::RawInput);
 
-/// A resource to check if we're on a mac, correctly detects on web too.
-#[derive(Resource)]
-pub struct IsMac(pub bool);
-
 /// A resource for accessing clipboard.
 ///
 /// The resource is available only if `manage_clipboard` feature is enabled.
@@ -557,21 +553,6 @@ impl Plugin for EguiPlugin {
         world.init_resource::<EguiClipboard>();
         world.init_resource::<EguiUserTextures>();
         world.init_resource::<EguiMousePosition>();
-        if !world.contains_resource::<IsMac>() {
-            let mut is_mac = cfg!(target_os = "macos");
-            #[cfg(target_arch = "wasm32")]
-            {
-                let window = web_sys::window().expect("window");
-
-                let nav = window.navigator();
-                let platform = nav.platform();
-                if let Ok(platform) = platform {
-                    is_mac = platform.starts_with("Mac");
-                }
-            }
-            log::info!(is_mac);
-            world.insert_resource(IsMac(is_mac));
-        }
 
         #[cfg(all(feature = "manage_clipboard", target_arch = "wasm32"))]
         app.add_startup_system(web_clipboard::startup_setup_web_events);
diff --git a/src/systems.rs b/src/systems.rs
index 7b5def730..c3aa20314 100644
--- a/src/systems.rs
+++ b/src/systems.rs
@@ -1,5 +1,5 @@
 use crate::{
-    EguiContext, EguiContextQuery, EguiInput, EguiMousePosition, EguiSettings, IsMac, WindowSize,
+    EguiContext, EguiContextQuery, EguiInput, EguiMousePosition, EguiSettings, WindowSize,
 };
 #[cfg(feature = "open_url")]
 use bevy::log;
@@ -71,14 +71,33 @@ pub struct ContextSystemParams<'w, 's> {
 
 /// Processes Bevy input and feeds it to Egui.
 pub fn process_input_system(
-    mut is_mac: Res<IsMac>,
     mut input_events: InputEvents,
     mut input_resources: InputResources,
     mut context_params: ContextSystemParams,
     egui_settings: Res<EguiSettings>,
     mut egui_mouse_position: ResMut<EguiMousePosition>,
     time: Res<Time>,
+    mut is_mac: Local<bool>,
 ) {
+    use std::sync::Once;
+    static START: Once = Once::new();
+
+    START.call_once(|| {
+        // run initialization here
+        *is_mac = cfg!(target_os = "macos");
+        #[cfg(target_arch = "wasm32")]
+        {
+            let window = web_sys::window().expect("window");
+
+            let nav = window.navigator();
+            let user_agent = nav.user_agent();
+            if let Ok(user_agent) = user_agent {
+                log::debug!("{:?}", user_agent);
+                *is_mac = user_agent.contains("Macintosh;");
+            }
+        }
+    });
+
     // This is a workaround for Windows. For some reason, `WindowFocused` event isn't fired
     // when a window is created.
     if let Some(event) = input_events.ev_window_created.iter().last() {
@@ -102,8 +121,8 @@ pub fn process_input_system(
     let win = input_resources.keyboard_input.pressed(KeyCode::LWin)
         || input_resources.keyboard_input.pressed(KeyCode::RWin);
 
-    let mac_cmd = if is_mac.0 { win } else { false };
-    let command = if is_mac.0 { win } else { ctrl };
+    let mac_cmd = if *is_mac { win } else { false };
+    let command = if *is_mac { win } else { ctrl };
 
     let modifiers = egui::Modifiers {
         alt,
diff --git a/src/web_clipboard.rs b/src/web_clipboard.rs
index a5b5b63f7..0e93c3746 100644
--- a/src/web_clipboard.rs
+++ b/src/web_clipboard.rs
@@ -49,17 +49,14 @@ fn setup_clipboard_copy(clipboard_channel: &mut WebChannel<WebEventCopy>) {
     let (tx, rx): (Sender<WebEventCopy>, Receiver<WebEventCopy>) = crossbeam_channel::bounded(1);
 
     let closure = Closure::<dyn FnMut(_)>::new(move |event: web_sys::ClipboardEvent| {
-        // TODO: maybe we should check if current canvas is selected ? not sure it's possible,
-        // but reacting to event at the document level will lead to problems if multiple games are on the same page.
         tx.try_send(WebEventCopy);
     });
 
-    // TODO: a lot of unwraps ; it's using documents because paste event set on a canvas do not trigger (also tested on firefox in vanilla javascript)
     let listener = closure.as_ref().unchecked_ref();
     web_sys::window()
-        .unwrap()
+        .expect("Could not retrieve web_sys::window()")
         .document()
-        .unwrap()
+        .expect("Could not retrieve web_sys window's document")
         .add_event_listener_with_callback("copy", listener)
         .expect("Could not add copy event listener.");
     closure.forget();
@@ -70,17 +67,14 @@ fn setup_clipboard_cut(clipboard_channel: &mut WebChannel<WebEventCut>) {
     let (tx, rx): (Sender<WebEventCut>, Receiver<WebEventCut>) = crossbeam_channel::bounded(1);
 
     let closure = Closure::<dyn FnMut(_)>::new(move |event: web_sys::ClipboardEvent| {
-        // TODO: maybe we should check if current canvas is selected ? not sure it's possible,
-        // but reacting to event at the document level will lead to problems if multiple games are on the same page.
         tx.try_send(WebEventCut);
     });
 
-    // TODO: a lot of unwraps ; it's using documents because paste event set on a canvas do not trigger (also tested on firefox in vanilla javascript)
     let listener = closure.as_ref().unchecked_ref();
     web_sys::window()
-        .unwrap()
+        .expect("Could not retrieve web_sys::window()")
         .document()
-        .unwrap()
+        .expect("Could not retrieve web_sys window's document")
         .add_event_listener_with_callback("cut", listener)
         .expect("Could not add cut event listener.");
     closure.forget();
@@ -91,8 +85,6 @@ fn setup_clipboard_paste(clipboard_channel: &mut WebChannel<WebEventPaste>) {
     let (tx, rx): (Sender<WebEventPaste>, Receiver<WebEventPaste>) = crossbeam_channel::bounded(1);
 
     let closure = Closure::<dyn FnMut(_)>::new(move |event: web_sys::ClipboardEvent| {
-        // TODO: maybe we should check if current canvas is selected ? not sure it's possible,
-        // but reacting to event at the document level will lead to problems if multiple games are on the same page.
         match event
             .clipboard_data()
             .expect("could not get clipboard data.")
@@ -108,12 +100,11 @@ fn setup_clipboard_paste(clipboard_channel: &mut WebChannel<WebEventPaste>) {
         info!("{:?}", event.clipboard_data())
     });
 
-    // TODO: a lot of unwraps ; it's using documents because paste event set on a canvas do not trigger (also tested on firefox in vanilla javascript)
     let listener = closure.as_ref().unchecked_ref();
     web_sys::window()
-        .unwrap()
+        .expect("Could not retrieve web_sys::window()")
         .document()
-        .unwrap()
+        .expect("Could not retrieve web_sys window's document")
         .add_event_listener_with_callback("paste", listener)
         .expect("Could not add paste event listener.");
     closure.forget();