Client-side persistent data or CSPD is a term used incomputing for storing data required byweb applications to complete internet tasks on theclient-side as needed rather than exclusively on theserver. As a framework it is one solution to the needs ofOccasionally connected computing or OCC.
A major challenge forHTTP as astateless protocol has been asynchronous tasks. TheAJAX pattern usingXMLHttpRequest was first introduced byMicrosoft in the context of theOutlook e-mail product.
The first CSPD were the'cookies' introduced by theNetscapeNavigator.ActiveX components which have entries in theWindows registry can also be viewed as a form ofclient-sidepersistence.[citation needed]