QUOTA_EXCEEDED_ERR: DOM Exception 22

I met this error when set data to sessionStorage. It means the data exceeded the browser limit. Most browsers have 2.5M or 5M limit per domain. Many developers assume that one character equals one byte, but this is not a safe assumption. Strings in JavaScript are UTF-16, so each character requires two bytes of memory. This means that while many browsers have a 5 MB limit, you can only store 2.5 M characters.

http://dev.w3.org/html5/webstorage/#disk-space recommends a 5M limit, but as of writing, Chrome 29, Safari 6 still use 2.5M limit, Firefox/Opera are ok. Also Firefox/Opera allows user to adjust the default value (about:config - search quota), Chrome/Safari/IE do not allow.

The practice is to handle this error in Javascript, and fallback to browser memory.

The error might look like as below
Uncaught QuotaExceededError: An attempt was made to add something to storage that exceeded the quota.