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+# Proposed WebIDL
+
+## Definition of the interface
+```webidl
+partial interface ServiceWorkerRegistration {
+  readonly attribute PeriodicSyncManager periodicSync;
+};
+
+[SecureContext, Exposed=(Window,Worker)]
+interface PeriodicSyncManager {
+  Promise<void> register(DOMString tag, BackgroundSyncOptions options);
+  Promise<void> unregister(DOMString tag);
+  Promise<sequence<DOMString>> getTags();
+};
+```
+
+## Definition of the Service Worker event
+```webidl
+partial interface ServiceWorkerGlobalScope {
+  attribute EventHandler onperiodicsync;
+};
+
+[Constructor(DOMString type, PeriodicSyncEventInit init), Exposed=ServiceWorker]
+interface SyncEvent : ExtendableEvent {
+  readonly attribute DOMString tag;
+};
+
+dictionary PeriodicSyncEventInit : ExtendableEventInit {
+  required DOMString tag;
+};
+```
+
+## Extensions to the Background Sync API
+```webidl
+dictionary BackgroundSyncOptions {
+  // …existing properties…
+  unsigned long long minInterval;
+};
+```