diff --git a/frontend_tests/node_tests/hotkey.js b/frontend_tests/node_tests/hotkey.js
index f8819e11cf..0d3ccfcc8d 100644
--- a/frontend_tests/node_tests/hotkey.js
+++ b/frontend_tests/node_tests/hotkey.js
@@ -33,6 +33,7 @@ $.fn.keydown = noop;
 $.fn.keypress = noop;
 
 var hotkey = zrequire('hotkey');
+zrequire('common');
 
 set_global('list_util', {
 });
diff --git a/static/js/common.js b/static/js/common.js
index 60fe8a042b..b074f437dd 100644
--- a/static/js/common.js
+++ b/static/js/common.js
@@ -100,6 +100,10 @@ exports.copy_data_attribute_value = function (elem, key) {
     elem.fadeIn(1000);
 };
 
+exports.has_mac_keyboard = function () {
+    return /Mac/i.test(navigator.userAgent);
+};
+
 return exports;
 
 }());
diff --git a/static/js/compose.js b/static/js/compose.js
index 8b32fa98d2..c8b334e47f 100644
--- a/static/js/compose.js
+++ b/static/js/compose.js
@@ -612,7 +612,7 @@ exports.handle_keydown = function (event, textarea) {
     var isLink = code === 76 && event.shiftKey;
 
     // detect command and ctrl key
-    var isCmdOrCtrl = /Mac/i.test(navigator.userAgent) ? event.metaKey : event.ctrlKey;
+    var isCmdOrCtrl = common.has_mac_keyboard() ? event.metaKey : event.ctrlKey;
 
     if ((isBold || isItalic || isLink) && isCmdOrCtrl) {
         var range = textarea.range();
diff --git a/static/js/hotkey.js b/static/js/hotkey.js
index 4401004fe0..5a4e05ef0f 100644
--- a/static/js/hotkey.js
+++ b/static/js/hotkey.js
@@ -128,7 +128,7 @@ exports.get_keydown_hotkey = function (e) {
         }
     }
 
-    var isCmdOrCtrl = /Mac/i.test(navigator.userAgent) ? e.metaKey : e.ctrlKey;
+    var isCmdOrCtrl = common.has_mac_keyboard() ? e.metaKey : e.ctrlKey;
     if (isCmdOrCtrl && !e.shiftKey) {
         hotkey = keydown_cmd_or_ctrl_mappings[e.which];
         if (hotkey) {
diff --git a/static/js/info_overlay.js b/static/js/info_overlay.js
index 9df13abe5a..3a9bb8b5a0 100644
--- a/static/js/info_overlay.js
+++ b/static/js/info_overlay.js
@@ -63,7 +63,7 @@ exports.set_up_toggler = function () {
 
     $(".informational-overlays .overlay-tabs").append(elem);
 
-    if (/Mac/i.test(navigator.userAgent)) {
+    if (common.has_mac_keyboard()) {
         adjust_mac_shortcuts();
     }
 
diff --git a/static/js/portico/help.js b/static/js/portico/help.js
index 31741528f3..ec9adba2f9 100644
--- a/static/js/portico/help.js
+++ b/static/js/portico/help.js
@@ -74,7 +74,7 @@ function render_code_sections() {
 
     highlight_current_article();
 
-    if (/Mac/i.test(navigator.userAgent)) {
+    if (common.has_mac_keyboard()) {
         adjust_mac_shortcuts();
     }
 
diff --git a/static/js/portico/tabbed-instructions.js b/static/js/portico/tabbed-instructions.js
index bfd77a9d1f..a965b57b8a 100644
--- a/static/js/portico/tabbed-instructions.js
+++ b/static/js/portico/tabbed-instructions.js
@@ -5,7 +5,7 @@ export function detect_user_os() {
     if (/iPhone|iPad|iPod/i.test(navigator.userAgent)) {
         return "ios";
     }
-    if (/Mac/i.test(navigator.userAgent)) {
+    if (common.has_mac_keyboard()) {
         return "mac";
     }
     if (/Win/i.test(navigator.userAgent)) {
diff --git a/static/js/ui.js b/static/js/ui.js
index 195b436b09..4c69b9105e 100644
--- a/static/js/ui.js
+++ b/static/js/ui.js
@@ -139,7 +139,7 @@ exports.get_hotkey_deprecation_notice = function (originalHotkey, replacementHot
 var shown_deprecation_notices = [];
 exports.maybe_show_deprecation_notice = function (key) {
     var message;
-    var isCmdOrCtrl = /Mac/i.test(navigator.userAgent) ? "Cmd" : "Ctrl";
+    var isCmdOrCtrl = common.has_mac_keyboard() ? "Cmd" : "Ctrl";
     if (key === 'C') {
         message = exports.get_hotkey_deprecation_notice('C', 'x');
     } else if (key === '*') {