Web Storage aka DOM Storage is a mechanism for client-side persistent data storage.
Web Storage is often compared to HTTP cookies, however they differ in some ways:
The Web Storage specification was designed as a better and more secure way of storing data on the client. There are two types of storage, Session Storage and Local Storage, exposed through the
localStorage global objects, respectively.
Session storage is intended for short-lived data and is available through the
sessionStorage attribute of the
window object (i.e. it is a global object).
Data stored in the
sessionStorage object is shared only with pages from the same domain opened in the same window/tab and does not persist after the window/tab is closed. Every time a user opens a page in a new window/tab, the browser creates a new session storage database.
The local storage mechanism allows to store data for more than a single session. Access to the local storage is available through the
localStorage global object. The
localStorage object is functionally identical to the
sessionStorage, except that data stored in the local storage area is persistent and not limited to the lifetime of the window/tab.
The local storage area is shared across multiple windows/tabs thus being suitable for use in multi-transaction scenarios.
Storage interface declares methods for storing, retrieving and deleting items. Both the
sessionStorage and the
localStorage are objects implementing the
Storage interface. The methods and properties are as follows:
storage event is fired whenever a storage area changes. The
storage event object has the following attributes:
The Web Storage specification is partially implemented in Internet Explorer 8, Firefox 3.5, Safari 4, Google Chrome 4 (support for the
sessionStorage object was added in version 5), and Opera 10.50. As of 14 July 2010, only Opera supports the DOM Storage events.