diff --git a/sw.js b/sw.js
index 8638c66..8b04cba 100644
--- a/sw.js
+++ b/sw.js
@@ -19,7 +19,9 @@ self.addEventListener('activate', event => {
     self.clients.claim();
 });
 
+const ORIGIN = self.location.origin;
 self.addEventListener('fetch', event => {
+    if (!event.request.url.startsWith(ORIGIN)) return;
     const url = new URL(event.request.url);
 
     // API: network first, fallback to cache