Stores one or more items in the storage area or updates stored items.

When you store or update a value using this API, the storage.onChanged event fires.

Note that when storing items in the sync storage area, the browser enforces quotas on the amount of data each extension can store. See Storage quotas for sync data.

This is an asynchronous function that returns a Promise.


let settingItem =<storageType>.set(
  keys             // object

<storageType> is one of the writable storage types — storage.local, storage.session, or storage.sync.



An object containing one or more key/value pairs to be stored. If an item is in storage, its value is updated.

Values can be primitive (such as a number, boolean, or string), Array, or Object types.

It's generally not possible to store other types, such as Function, Date, RegExp, Set, Map, ArrayBuffer, and so on. Some unsupported types restore as an empty object, while others cause set() to throw an error. The behavior is browser-specific.

Note: If you want to remove keys from storage, use storage.storageArea.remove. If you want to overwrite a value with a void value, use null, i.e., key: null.

Return value

A Promise that is fulfilled with no arguments if the operation succeeds. If the operation fails, the promise is rejected with an error message.


function setItem() {

function gotKitten(item) {
  console.log(`${} has ${item.kitten.eyeCount} eyes`);

function gotMonster(item) {
  console.log(`${} has ${} eyes`);

function onError(error) {

// define 2 objects
let monster = {
  name: "Kraken",
  tentacles: true,
  eyeCount: 10,

let kitten = {
  name: "Moggy",
  tentacles: false,
  eyeCount: 2,

// store the objects{ kitten, monster }).then(setItem, onError);"kitten").then(gotKitten, onError);"monster").then(gotMonster, onError);

Browser compatibility

BCD tables only load in the browser

Note: This API is based on Chromium's API. This documentation is derived from storage.json in the Chromium code.