Objectively, it is measurable time, in milliseconds, it takes for the web page or web application to be downloaded, painted in the user's web browser, and become responsive and interactive. It is the frames per second and times the main thread is not available for user interactions. Subjectively, it is the user's perception of whether the time it takes between the time the user requests the content and the time until the user feels the content requested is available and usable feels slow or fast.