diff --git a/Libraries/LibWeb/ServiceWorker/CacheStorage.cpp b/Libraries/LibWeb/ServiceWorker/CacheStorage.cpp
index 1d95b7a88b2..22a2fd56f08 100644
--- a/Libraries/LibWeb/ServiceWorker/CacheStorage.cpp
+++ b/Libraries/LibWeb/ServiceWorker/CacheStorage.cpp
@@ -30,4 +30,11 @@ GC::Ref<WebIDL::Promise> CacheStorage::open(String const&)
     return WebIDL::create_rejected_promise(realm(), WebIDL::NotSupportedError::create(realm(), "CacheStorage.open() is not yet implemented"_string));
 }
 
+// https://w3c.github.io/ServiceWorker/#cache-storage-has
+GC::Ref<WebIDL::Promise> CacheStorage::has(String const&)
+{
+    dbgln("FIXME: CacheStorage::has() is not implemented yet");
+    return WebIDL::create_rejected_promise(realm(), JS::Value(false));
+}
+
 }
diff --git a/Libraries/LibWeb/ServiceWorker/CacheStorage.h b/Libraries/LibWeb/ServiceWorker/CacheStorage.h
index 5b9af542ad8..e3479725060 100644
--- a/Libraries/LibWeb/ServiceWorker/CacheStorage.h
+++ b/Libraries/LibWeb/ServiceWorker/CacheStorage.h
@@ -17,6 +17,7 @@ class CacheStorage : public Bindings::PlatformObject {
     GC_DECLARE_ALLOCATOR(CacheStorage);
 
 public:
+    GC::Ref<WebIDL::Promise> has(String const& cache_name);
     GC::Ref<WebIDL::Promise> open(String const& cache_name);
 
 private:
diff --git a/Libraries/LibWeb/ServiceWorker/CacheStorage.idl b/Libraries/LibWeb/ServiceWorker/CacheStorage.idl
index b214bab1c06..2d3f7382209 100644
--- a/Libraries/LibWeb/ServiceWorker/CacheStorage.idl
+++ b/Libraries/LibWeb/ServiceWorker/CacheStorage.idl
@@ -4,7 +4,7 @@
 [SecureContext, Exposed=(Window,Worker)]
 interface CacheStorage {
     //[NewObject] Promise<(Response or undefined)> match(RequestInfo request, optional MultiCacheQueryOptions options = {});
-    //[NewObject] Promise<boolean> has(DOMString cacheName);
+    [NewObject] Promise<boolean> has(DOMString cacheName);
     [NewObject] Promise<Cache> open(DOMString cacheName);
     //[NewObject] Promise<boolean> delete(DOMString cacheName);
     //[NewObject] Promise<sequence<DOMString>> keys();