diff --git a/api/PerformanceObserver.json b/api/PerformanceObserver.json
index 834115e8b647c..2b5c8c319225a 100644
--- a/api/PerformanceObserver.json
+++ b/api/PerformanceObserver.json
@@ -74,6 +74,43 @@
             "standard_track": true,
             "deprecated": false
           }
+        },
+        "droppedEntriesCount": {
+          "__compat": {
+            "description": "<code>droppedEntriesCount()</code> parameter",
+            "spec_url": "https://w3c.github.io/performance-timeline/#dom-performanceobservercallbackoptions-droppedentriescount",
+            "support": {
+              "chrome": {
+                "version_added": "95"
+              },
+              "chrome_android": "mirror",
+              "edge": "mirror",
+              "firefox": {
+                "version_added": false
+              },
+              "firefox_android": "mirror",
+              "ie": {
+                "version_added": false
+              },
+              "nodejs": {
+                "version_added": false
+              },
+              "oculus": "mirror",
+              "opera": "mirror",
+              "opera_android": "mirror",
+              "safari": {
+                "version_added": false
+              },
+              "safari_ios": "mirror",
+              "samsunginternet_android": "mirror",
+              "webview_android": "mirror"
+            },
+            "status": {
+              "experimental": true,
+              "standard_track": true,
+              "deprecated": false
+            }
+          }
         }
       },
       "worker_support": {