While cookies are very useful for storing basic data, they are limited by the fact that Web browsers are not required to keep more than 20 cookies per Web server or more than 4KB of data per cookie (including both name and value).
In addition, they are sent to the Web server with every HTTP request, which is a waste of resources.
HTML5 provides a solution for these problems with the Local Storage APIs, which are covered in a separate specification to the main HTML5 document. This set of APIs allows developers to store information on the visitor's computer while remaining reasonably confident that they will still be there at a later date. In addition, the information is accessible at any point (even after the page has rendered) and is not loaded automatically with each HTTP request.
The specification includes same-origin restrictions, which prevent Web sites from reading or changing data stored by other Web sites.
Most browsers store Web pages in local cache, allowing them to be viewed even if the user is
HTML5 provides support for offline applications, where the browser downloads all the files necessary to use the application offline, and when the user uses the application offline, the browser can allow any changes made in the process to be uploaded to the server when they reconnect to the Internet.