When we use forward method request is transfer to other resource within the same server for further processing.
In case of sendRedirect request is transfer to another resource to different domain or different server for futher processing.
In case of forward Web container handle all process internally and client or browser is not involved.
When you use SendRedirect container transfers the request to client or browser so url given inside the sendRedirect method is visible as a new request to the client.
When forward is called on requestdispatherobject we pass request and response object so our old request object is present on new resource which is going to process our request
In case of SendRedirect call old request and response object is lost because it’s treated as new request by the browser.
Visually we are not able to see the forwarded address, its is transparent
In address bar we are able to see the new redirected address it’s not transparent.
Using forward () method is faster then send redirect.
SendRedirect is slower because one extra round trip is required beasue completely new request is created and old request object is lost.Two browser request requird.
When we redirect using forward and we want to use same data in new resource we can use request.setAttribute () as we have request object available.
But in sendRedirect if we want to use we have to store the data in session or pass along with the URL.