Varies by brand. If, to install it, you have to get to a screw under a "Warranty Void If..." label, you have your answer. I usually keep the original drive so as to be able to restore the computer to stock. That also allows me to have the ability to test to see if the problem requiring warranty service is drive or software related, or a real hardware problem elsewhere. Make sure to use the right tools when doing the swap or installation and refer to repair guides at iFixit.com or YouTube.