diff --git a/serviceworker.js b/serviceworker.js
new file mode 100644
index 0000000..0dcb79a
--- /dev/null
+++ b/serviceworker.js
@@ -0,0 +1,39 @@
+var cacheName = 'takarasagashi-2025_1223';
+var filesToCache = [
+    './',
+    './loc-chase2.html',
+    './loc-chase2.js',
+    './pwa-sample-192.png'
+    './pwa-sample/ico'
+];
+self.addEventListener('install', function(event) {
+    console.log('ServiceWorker installing');
+    event.waitUntil(
+	caches.open(cacheName).then(function(cache) {
+	    console.log('Service Worker caching app shell');
+	    return cache.addAll(filesToCache);
+	})
+    );
+});
+self.addEventListener('activate', function(event) {
+    console.log('Service Worker activating');
+    event.waitUntil(
+	caches.keys().then(function(keyList) {
+	    return Promise.all(keyList.map(function(key) {
+		if (key !== cacheName) {
+		    console.log('Service Worker removing old cache', key);
+		    return caches.delete(key);
+		}
+	    }));
+	})
+    );
+    return self.clients.claim();
+});
+self.addEventListener('fetch', function(event) {
+    console.log('Service Worker fetching', event.request.url);
+    event.respondWith(
+	caches.match(event.request).then(function(response) {
+	    return response || fetch(event.request);
+	})
+    );
+});