The HTML5 Web Storage standard was developed to allow sites to store larger amounts of data (like 5-10 MB) than was previously allowed by cookies (like 4KB). localStorage is awesome because it’s supported in all modern browsers (Chrome, Firefox 3.5+, Safari 4+, IE 8+, etc.).
The standard anticipated that sites might abuse this feature and advised that browsers limit the total amount of storage space that each origin could use.
- Feross Aboukhadijeh | feross.org