Web Storage

Web Storage (also called DOM Storage or super cookies) is a technique for Web applications that are stored in a web browser with the data. DOM storage supports persistent data storage, like cookies, as well as the local session specific storage.

DOM Storage is standardized by the World Wide Web Consortium (W3C). Originally it was part of the HTML5 specification, but has now been spun off into a separate specification. Currently, DOM Storage of Internet Explorer 8, Mozilla -based browsers (eg Firefox 2 , officially since 3.5) supports, Safari 4, Google Chrome 4 and Opera 10:50.

Features

DOM Storage can be described as a development of cookies ("super - cookies" ) are considered. The technique provides much greater storage capacity ( 5MB per domain in Firefox, 10MB per storage area in Internet Explorer) and better development interfaces. In some respects, however, it differs from cookies.

Client - side interface

In contrast to cookies, both server and client can access the DOM Storage is fully controlled by the client. There are not transmitted in this with every HTTP request data to the server and a web server can not write data directly in the DOM Storage also. Access is only via scripts on the website.

Storage

DOM Storage offers two different types of storage: local (local storage) and session - specific ( sessionStorage ). They differ in scope and duration.

Local storage

Data that is stored locally so-called Local Shared Objects ( LSO), are associated with a domain and remain even after closing the browser exist. All scripts on a domain, from which the data was stored, may access the data.

In Mozilla Firefox the data in the database file are stored webappsstore.sqlite. With a suitable program the SQLite3 file can be viewed. There are browser add-ons that have arisen for the purpose that we can delete this information from your system again, even automated, eg with Better Privacy. About typing " about: config" in the address bar, the value of dom.storage.enabled can of true changed to false, and DOM Storage objects are thus switched off.

Session - specific storage

Session - specific data stored are linked to the browser window and limited to this. Stored data will be deleted when you close the browser window. This technique provides the ability to run multiple instances of the same application running in various windows, without causing mutual interference, which does not support cookies.

Data model

DOM Storage stores data in an associative array where the keys and values ​​are strings. About an additional programming interface for accessing structured data, possibly based on SQL, is currently being discussed within the Web Applications Working Group of the W3C.

Naming

The design of the W3C speaks of " Web Storage ", although " DOM Storage" has become the more common name.

The abbreviation " DOM " in " DOM Storage" is not in direct connection to the Document Object Model: " The term DOM refers to the application interfaces that are scripts in Web applications, and does not necessarily imply the existence of an actual Document object [ ... ] "

Similar technologies

  • HTTP cookies
  • Local Shared Objects in Flash
  • Google Gears for IE, Firefox, Safari and Windows Mobile
Persistence (computer science) Magic cookie Gears (software)
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