Correlation is the process of taking values from a server response and then storing them in a VARIABLE that will be used in SUBSEQUENT requests. Correlation is the way of ACQUIRING some value from one step's response and transferring it to another step's request. It catches and saves the server's dynamic answer before passing it on to subsequent requests. When a response returns different data for each ITERATING request, it is termed dynamic, and this can sometimes affect subsequent requests. Correlation is a critical step in the performance load test SCRIPTING process since if it isn't handled properly, the script will become ineffective. One of the most fundamental components of scripting is a correlation. It retrieves dynamic data from previous requests and posts it to new requests.

For example, if you need to test any login feature and need to use the session ID or the cookie ID, you can obtain the values from the login page's GET response and use them dynamically for login in a POST request.