Cookies and website data
Websites often store cookies and other data on your Mac. This data may include information you have provided, such as your name, email address and your settings. The data helps websites identify you so when you return, the site can provide services and information that might be of interest to you.
You can change your settings so Safari always blocks or always accepts cookies and other website data.
Choose Safari > Settings, click Advanced, then select or deselect “Block all cookies”.