a - rel : noopener | noreferrer | nofollow

This prevent the external page gaining any access to the original page and also won't pass any referrer information to the external page.

• Willing to protect your site users from potentially malicious external links (noopener)
• Unwilling to appear in a website’s analytics data as Referred traffic (noreferrer)
• Unwilling to endorse the content or creator you’re linking to (nofollow)