diff --git a/.changeset/chilly-moons-play.md b/.changeset/chilly-moons-play.md
new file mode 100644
index 00000000000..1d1db3c15c6
--- /dev/null
+++ b/.changeset/chilly-moons-play.md
@@ -0,0 +1,5 @@
+---
+'@firebase/util': patch
+---
+
+fix: browser detection (detect either window or web worker)
diff --git a/packages/util/src/environment.ts b/packages/util/src/environment.ts
index f2afaede0f1..9c2024232d4 100644
--- a/packages/util/src/environment.ts
+++ b/packages/util/src/environment.ts
@@ -77,7 +77,14 @@ export function isNode(): boolean {
  * Detect Browser Environment
  */
 export function isBrowser(): boolean {
-  return typeof self === 'object' && self.self === self;
+  return typeof window !== 'undefined' || isWebWorker();
+}
+
+/**
+ * Detect Web Worker context
+ */
+export function isWebWorker(): boolean {
+  return typeof WorkerGlobalScope !== 'undefined' && self instanceof WorkerGlobalScope;
 }
 
 /**