In March 2019 Apple launched Intelligent Tracking Prevention 2.1(ITP) which now affects both first, and third-party cookies when using the Safari browser on Apple devices. This feature blocks third-party cookies entirely and limits first-party cookies from tracking cross-domain data of users. Client-side cookies are also capped to 7 days of storage. ITP 2.1 will affect/limit ad targeting strategies for Safari users as tracking these users will not be as efficient- you may see a surge in unique visitors as analytical tools may be counting one user as two unique users if they are to access the domain after 7 days. This could also inflate the number of unique visitors that brands see in their analytics figures.