What is HTML5 Storage?
The HTML5 (web) storage spec is a standardized way of providing larger amounts of client-side storage and of more appropriately “partitioning” session storage and locally persistent storage. The HTML5 spec also provides for storage events to be generated and handled by interested listeners. The full impact of these features provided by HTML5 storage can best be seen by looking at client-side storage in the non-HTML5 world.
Without HTML5, client-side storage for web applications is limited to the tiny storage provided by cookies (4KB per cookie, 20 cookies per domain) unless proprietary storage schemes are used, such as Flash local shared objects or Google Gears. If cookies are used they provide both session and locally persistent storage at the same time, and are accessible by all browser windows and tabs. Domain cookies are sent with every request to that domain, which consumes bandwidth. The “mechanics” of processing cookies are also a bit cumbersome.
In contrast, HTML5 storage provides a much larger initial local storage (5MB per domain), unlimited session storage (limited only by system resources) and successfully partitions local and session storage so that only the data you want to persist is persisted in local storage and data you want to be transient stays transient. Moreover, session storage is only accessible from its originating tab or window; it is not shared between all browser windows and tabs. Accessing session and local storage is simple, consisting in simple reads and writes of key-value strings. Finally, local and session storage are client-side only; they are not sent with requests.