The procedure for provisioning managed storage varies between browsers. For Chrome instructions, see the "Manifest for storage areas" article.

For Firefox, you need to create a JSON manifest file in a specific format and location. For the details of manifest syntax and location, see Native manifests.

Here's an example manifest:

{
  "name": "[email protected]",
  "description": "ignored",
  "type": "storage",
  "data": {
    "colour": "management thinks it should be blue!"
  }
}

Given this manifest, the favourite-colour extension could access the data using code like this:

let storageItem = browser.storage.managed.get('colour');
storageItem.then((res) => {
  console.log(`Managed colour is: ${res.colour}`);
});

The managed object implements the methods defined on the storage.StorageArea type:

storage.managed.get()

Retrieves one or more items from the storage area.

storage.managed.getBytesInUse()

Gets the amount of storage space (in bytes) used for one or more items in the storage area.

The managed object implements the events defined on the storage.StorageArea type:

storage.managed.onChanged

Fires when one or more items in the storage area change.

• favourite-colour