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Window: storage event

files/en-us/web/api/window/storage_event/index.md

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{{APIRef}}

The storage event of the {{domxref("Window")}} interface fires when another document that shares the same storage area (either {{domxref("Window/localStorage", "localStorage")}} or {{domxref("Window/sessionStorage", "sessionStorage")}}) as the current window updates that storage area. The event is not fired on the window that made the change.

  • For localStorage, the event is fired in all other {{Glossary("browsing context", "browsing contexts")}} that are in the same origin as the initiating document. This includes other tabs with the same origin.
  • For sessionStorage, the event is fired in all other {{Glossary("browsing context", "browsing contexts")}} that are in the same origin and the same top-level browsing context as the initiating document. This only includes embedded iframes, if any, in the same tab, and not other tabs.

This event is not cancelable and does not bubble.

Syntax

Use the event name in methods like {{domxref("EventTarget.addEventListener", "addEventListener()")}}, or set an event handler property.

js-nolint
addEventListener("storage", (event) => { })

onstorage = (event) => { }

Event type

A {{domxref("StorageEvent")}}. Inherits from {{domxref("Event")}}.

{{InheritanceDiagram("StorageEvent")}}

Event properties

  • {{domxref("StorageEvent.key", "key")}} {{ReadOnlyInline}}
    • : Returns a string with the key for the storage item that was changed. The key attribute is null when the change is caused by the storage clear() method.
  • {{domxref("StorageEvent.newValue", "newValue")}} {{ReadOnlyInline}}
    • : Returns a string with the new value of the storage item that was changed. This value is null when the change has been invoked by storage clear() method, or the storage item has been removed from the storage.
  • {{domxref("StorageEvent.oldValue", "oldValue")}} {{ReadOnlyInline}}
    • : Returns a string with the original value of the storage item that was changed. This value is null when the storage item has been newly added and therefore doesn't have any previous value.
  • {{domxref("StorageEvent.storageArea", "storageArea")}} {{ReadOnlyInline}}
    • : Returns a {{DOMxRef("Storage")}} object that represents the storage object that was affected.
  • {{domxref("StorageEvent.url", "url")}} {{ReadOnlyInline}}
    • : Returns string with the URL of the document whose storage changed.

Event handler aliases

In addition to the Window interface, the event handler property onstorage is also available on the following targets:

  • {{domxref("HTMLBodyElement")}}
  • {{domxref("HTMLFrameSetElement")}}
  • {{domxref("SVGSVGElement")}}

Examples

Log the sampleList item to the console when the storage event fires:

js
window.addEventListener("storage", () => {
  // When local storage changes, dump the list to
  // the console.
  console.log(JSON.parse(window.localStorage.getItem("sampleList")));
});

The same action can be achieved using the onstorage event handler property:

js
window.onstorage = () => {
  // When local storage changes, dump the list to
  // the console.
  console.log(JSON.parse(window.localStorage.getItem("sampleList")));
};

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also