Overview

This API has been optimized to meet the specific storage needs of extensions. It provides the same storage capabilities as the localStorage API with the following key differences:

• User data can be automatically synced with Chrome sync (using storage.sync).
• Your extension's content scripts can directly access user data without the need for a background page.
• A user's extension settings can be persisted even when using split incognito behavior.
• It's asynchronous with bulk read and write operations, and therefore faster than the blocking and serial localStorage API.
• User data can be stored as objects (the localStorage API stores data in strings).

Manifest

You must declare the "storage" permission in the extension manifest to use the storage API. For example:

{
  "name": "My extension",
  ...
  "permissions": [
    "storage"
  ],
  ...
}

Usage

To store user data for your extension, you can use either storage.sync or storage.local. When using storage.sync, the stored data will automatically be synced to any Chrome browser that the user is logged into, provided the user has sync enabled.

When Chrome is offline, Chrome stores the data locally. The next time the browser is online, Chrome syncs the data. Even if a user disables syncing, storage.sync will still work. In this case, it will behave identically to storage.local.

Confidential user information should not be stored! The storage area isn't encrypted.

Storage and throttling limits

chrome.storage is not a big truck. It's a series of tubes. And if you don't understand, those tubes can be filled, and if they are filled when you put your message in, it gets in line, and it's going to be delayed by anyone that puts into that tube enormous amounts of material.

For details on the current limits of the storage API, and what happens when those limits are exceeded, please see the quota information for sync and local.

Examples

The following example checks for CSS code saved by a user on a form, and if found, stores it.

function saveChanges() {
  // Get a value saved in a form.
  var theValue = textarea.value;
  // Check that there's some code there.
  if (!theValue) {
    message('Error: No value specified');
    return;
  }
  // Save it using the Chrome extension storage API.
  chrome.storage.sync.set({'value': theValue}, function() {
    // Notify that we saved.
    message('Settings saved');
  });
}

If you're interested in tracking changes made to a data object, you can add a listener to its onChanged event. Whenever anything changes in storage, that event fires. Here's sample code to listen for saved changes:

chrome.storage.onChanged.addListener(function(changes, namespace) {
  for (key in changes) {
    var storageChange = changes[key];
    console.log('Storage key "%s" in namespace "%s" changed. ' +
                'Old value was "%s", new value is "%s".',
                key,
                namespace,
                storageChange.oldValue,
                storageChange.newValue);
  }
});