But from a monitoring perspective, they are very different. The server on which the requested Web site lives must acknowledge the browser's request to view the Web site.
Response time is a product of server performance.
Therefore, those tools that track your server activities are the tools that measure response times. Your ability to access and interpret response-time data will depend upon your server model, that is, where your Web site resides. Get the PDF file. Your Web Host. If you use a hosting service, response-time measurements should be part of the data available to you.