As time passes, you will notice that the number of programs that are automatically launched at startup will significantly grow, which in the process can drastically increase the time required for your system to fully boot. This tutorial explains how to track down the software you rarely or never use, and remove them from the startup routine of your Mac.
Click on the Apple menu > System Preferences > Users & Groups. Select the user account of your selection (if multiple) and click on the Login Items tab to view all your startup programs. To permanently remove a program from the startup routine of your Mac, simply select it and click on the "-" button.
NB: you can if you want to add new applications (your favorite instant messaging software, a cloud sharing/storage app...) to the list using the "+".