Some would prefer to have things automated, and as soon as they start their mac, they would need a few applications to automatically load and login them into it. But many would prefer against it. Opening the app, logging into it without the user even knowing about it, is problematic many times. For example, Skype comes with the default option of opening when the mac system starts up. But there is an option in the system preferences in mac, which can help you prevent Skype or any other application from opening at the startup of the Mac OS –
Open System Preferences, by either searching in Spotlight, or by going to the Apple Menu, in the left top corner. This should open the system preferences section of your mac.
In the system preferences, you will see a big list of sections which would have the ‘Accounts‘ under ‘System‘. Open that –
In the accounts tab, select the account you are using, and then select “Login Items“. That would show you the applications that will open automatically when you log in. To hide an application, you just have to select the Hide checkbox beside it. And your problem is solved. You won’t see the app opening during startup.