diff --git a/packages/core/src/index.html b/packages/core/src/index.html
index 53c465abec05..1b1a530817c4 100644
--- a/packages/core/src/index.html
+++ b/packages/core/src/index.html
@@ -36,6 +36,17 @@
                 background-color: var(--general-main-1);
             }
         </style>
+        <script type="text/javascript">
+            !(function () {
+                if ('PerformanceLongTaskTiming' in window) {
+                    var g = (window.__tti = { e: [] });
+                    g.o = new PerformanceObserver(function (l) {
+                        g.e = g.e.concat(l.getEntries());
+                    });
+                    g.o.observe({ entryTypes: ['longtask'] });
+                }
+            })();
+        </script>
         <script type="text/javascript">
             var ui_store = localStorage.getItem('ui_store');
             var l = window.location;