diff --git a/README.md b/README.md
index 03b012b..7028de4 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,12 @@ The function looks for a `GOOGLE_API_KEY` value using `process.env` in Node or
 `Deno.env.get` in Netlify's Edge runtime. When the variable is absent, a default
 API key is used.
 
+### Caching
+
+Responses are cached for 30 seconds using the Edge Cache API when available. If
+the runtime does not support the cache API, the function skips caching but still
+returns live data.
+
 ### Running tests
 
 ```sh
diff --git a/netlify/edge-functions/opensheet.js b/netlify/edge-functions/opensheet.js
index d03a26c..681096f 100644
--- a/netlify/edge-functions/opensheet.js
+++ b/netlify/edge-functions/opensheet.js
@@ -34,13 +34,15 @@ export default async function handler(request, context) {
 
   // Try cache first (Edge Cache API)
   const cacheKey = `https://sheets-json-api.netlify.app/${id}/${encodeURIComponent(sheet)}`;
-  const cache = caches.default;
-  const cachedResponse = await cache.match(cacheKey);
-  if (cachedResponse) {
-    console.log(`Serving from cache: ${cacheKey}`);
-    return cachedResponse;
-  } else {
-    console.log(`Cache miss: ${cacheKey}`);
+  const cache = globalThis.caches?.default;
+  if (cache) {
+    const cachedResponse = await cache.match(cacheKey);
+    if (cachedResponse) {
+      console.log(`Serving from cache: ${cacheKey}`);
+      return cachedResponse;
+    } else {
+      console.log(`Cache miss: ${cacheKey}`);
+    }
   }
 
   // Normalize sheet (handle '+' and decode)
@@ -104,7 +106,9 @@ export default async function handler(request, context) {
   });
 
   // Write to cache in the background
-  context.waitUntil(cache.put(cacheKey, apiResponse.clone()));
+  if (cache) {
+    context.waitUntil(cache.put(cacheKey, apiResponse.clone()));
+  }
 
   return apiResponse;
 }
diff --git a/test/opensheet.test.js b/test/opensheet.test.js
index f30ec06..0b5ce88 100644
--- a/test/opensheet.test.js
+++ b/test/opensheet.test.js
@@ -40,6 +40,21 @@ test('falls back to static content on root path', async () => {
   assert.strictEqual(res, nextResponse);
 });
 
+test('works when cache API is unavailable', async () => {
+  delete globalThis.caches;
+
+  const originalFetch = globalThis.fetch;
+  globalThis.fetch = async () =>
+    new Response(JSON.stringify({ values: [["name"], ["Ada"]] }));
+
+  const req = new Request('https://example.com/test-sheet/Sheet1');
+  const res = await handler(req, context);
+  const data = await res.json();
+  assert.deepStrictEqual(data, [{ name: 'Ada' }]);
+
+  globalThis.fetch = originalFetch;
+});
+
 test('uses Deno env when process env missing', async () => {
   const originalKey = process.env.GOOGLE_API_KEY;
   delete process.env.GOOGLE_API_KEY;