View State data is stored in a hidden field called “__VIEWSTATE” on a Web page. It stored data in Base64 String encoded format which can be further decoded. Sample hidden field looks like below:
<input type=”hidden” name=”__VIEWSTATE” id=”__VIEWSTATE” value=”/wEPDwUKMTM1ODM3Nj…….” />
This single hidden field contains all the viewstate values for all the page controls.