diff --git a/packages/app-check/src/debug.ts b/packages/app-check/src/debug.ts
index 2e823d4d17d..da6cffbfcc4 100644
--- a/packages/app-check/src/debug.ts
+++ b/packages/app-check/src/debug.ts
@@ -17,18 +17,13 @@
 
 import { getDebugState } from './state';
 import { readOrCreateDebugTokenFromStorage } from './storage';
-import { Deferred } from '@firebase/util';
+import { Deferred, getGlobal } from '@firebase/util';
 
 declare global {
-  interface Window {
-    /**
-     * When it is a string, we treat it as the debug token and give it to consumers as the app check token
-     * When it is `true`, we will try to read the debug token from the indexeddb,
-     *      if it doesn't exist, create one, print it to console, and ask developers to register it in the Firebase console.
-     * When it is `undefined`, `false` or any unsupported value type, the SDK will operate in production mode
-     */
-    FIREBASE_APPCHECK_DEBUG_TOKEN?: boolean | string;
-  }
+  // var must be used for global scopes
+  // https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-4.html#type-checking-for-globalthis
+  // eslint-disable-next-line no-var
+  var FIREBASE_APPCHECK_DEBUG_TOKEN: boolean | string | undefined;
 }
 
 export function isDebugMode(): boolean {
@@ -50,9 +45,10 @@ export async function getDebugToken(): Promise<string> {
 }
 
 export function initializeDebugMode(): void {
+  const globals = getGlobal();
   if (
-    typeof self.FIREBASE_APPCHECK_DEBUG_TOKEN !== 'string' &&
-    self.FIREBASE_APPCHECK_DEBUG_TOKEN !== true
+    typeof globals.FIREBASE_APPCHECK_DEBUG_TOKEN !== 'string' &&
+    globals.FIREBASE_APPCHECK_DEBUG_TOKEN !== true
   ) {
     return;
   }
@@ -62,8 +58,8 @@ export function initializeDebugMode(): void {
   const deferredToken = new Deferred<string>();
   debugState.token = deferredToken;
 
-  if (typeof self.FIREBASE_APPCHECK_DEBUG_TOKEN === 'string') {
-    deferredToken.resolve(self.FIREBASE_APPCHECK_DEBUG_TOKEN);
+  if (typeof globals.FIREBASE_APPCHECK_DEBUG_TOKEN === 'string') {
+    deferredToken.resolve(globals.FIREBASE_APPCHECK_DEBUG_TOKEN);
   } else {
     deferredToken.resolve(readOrCreateDebugTokenFromStorage());
   }
diff --git a/packages/database/src/realtime/WebSocketConnection.ts b/packages/database/src/realtime/WebSocketConnection.ts
index 6038f473a7d..81c91a95093 100644
--- a/packages/database/src/realtime/WebSocketConnection.ts
+++ b/packages/database/src/realtime/WebSocketConnection.ts
@@ -166,9 +166,16 @@ export class WebSocketConnection implements Transport {
           }
         };
 
+        // If using Node with admin creds, AppCheck-related checks are unnecessary.
+        // It will send the authorization token.
         if (this.nodeAdmin) {
           options.headers['Authorization'] = this.authToken || '';
         } else {
+          // If using Node without admin creds (which includes all uses of the
+          // client-side Node SDK), it will send an AppCheck token if available.
+          // Any other auth credentials will eventually be sent after the connection
+          // is established, but aren't needed here as they don't effect the initial
+          // request to establish a connection.
           options.headers['X-Firebase-AppCheck'] = this.appCheckToken || '';
         }
 
diff --git a/packages/util/src/environment.ts b/packages/util/src/environment.ts
index 92fdd4478c7..f2ad5306583 100644
--- a/packages/util/src/environment.ts
+++ b/packages/util/src/environment.ts
@@ -189,3 +189,20 @@ export function areCookiesEnabled(): boolean {
   }
   return true;
 }
+
+/**
+ * Polyfill for `globalThis` object.
+ * @returns the `globalThis` object for the given environment.
+ */
+export function getGlobal(): typeof globalThis {
+  if (typeof self !== 'undefined') {
+    return self;
+  }
+  if (typeof window !== 'undefined') {
+    return window;
+  }
+  if (typeof global !== 'undefined') {
+    return global;
+  }
+  throw new Error('Unable to locate global object.');
+}