Stores one or more items in the storage area, or update existing items.

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

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> will be one of the writable storage types — storage.sync or storage.local.



An object containing one or more key/value pairs to be stored in storage. If an item already exists, its value will be 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 of these unsupported types will restore as an empty object, and some cause set() to throw an error. The exact behavior here is browser-specific.

Return value

A Promise that will be fulfilled with no arguments if the operation succeeded. If the operation failed, the promise will be rejected with an error message.

Browser compatibility

BCD tables only load in the browser


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);

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