Same issue. Lack of docs around this is pretty terrible. The best I've found is this (search for 7-day): https://webkit.org/blog/10218/full-third-party-cookie-blocking-and-more/ Additionally, Safari desktop doesn't appear to support Add to Home Screen...so that seems to imply that people using a offline first web app on Safari Desktop will always be at risk for data loss. Unacceptable! I have experimented with using the StorageManager "persist" option with Safari Desktop in order to mark persistence as "protected". However, it appears this gets reset when the browser closes and again there's a lack of documentation so it's not even clear if this would help protect against the 7-day ITP timer. Without more documentation and clear direction from Apple, I'm basically forced to tell my users not to use Desktop Safari :(