Retrieves a value previously stored by a call to sessions.setWindowValue.

You can retrieve a value from a window even over a close/restore cycle: meaning that if you set a value, then the user closes the window, then restores the window using the browser's "restore window" feature (for example, by pressing Control+Shift+N), then you will be able to retrieve the value from the restored window. Note, though, that a restored window does not get the same ID as the original, so the ID you pass into getWindowValue() will be different from the ID you passed into setWindowValue(), even though they both refer to the same window.

This is an asynchronous function that returns a Promise.


let retrieving = browser.sessions.getWindowValue(
  windowId,    // integer
  key          // string



integer. ID of the window whose data you are trying to retrieve. Error is thrown if ID is invalid.


string. Key identifying the particular value to retrieve. This needs to match the key previously given in sessions.setWindowValue.

Return value

A Promise that will be resolved with the value if it exists, or undefined if it does not exist. If the call failed (for example, because the window ID could not be found) then the promise will be rejected with an error message.

Browser compatibility

BCD tables only load in the browser


Log the value of "my-key" for all newly created windows (this will include any windows that have been restored):

function onGetResolved(r) {
  console.log(`success: ${r}`);

function onGetRejected(e) {
  console.log(`error: ${e}`);
} => {
    .getWindowValue(, "my-key")
    .then(onGetResolved, onGetRejected);