ECSP (Embedded Client Side Paradata) is a system based on HTML, JavaScript as well as CSS script, which can be implemented in the online survey software EFS-Survey/Unipark in order to capture and store client side paradata together with substantive and metadata in one database. Based on “pixel perfect” displaying of survey pages in EFS-Survey/Unipark ECSP provides the ability to capture the full paradata regardless of the used browser, as well as the used operating system. ECSP is, furthermore, capable to identify movements of the mouse cursor, mouse clicks, keystrokes, zooming, scrolling, browser resolution, as well as losing focus of the survey. All these events are provided with timestamps and are stored together with measurements of processing and transferring times.