Provide a reliable experience when external sites serve content from your org in an iFrame. Target a Content Security Policy (CSP) header under 12 KB to reduce failures caused by infrastructure limits on HTTP header size. Customers report issues as headers approach 16 KB, and third-party processing can increase header size.
Where: This change applies to Lightning Experience and Salesforce Classic in Contact Manager, Group, Professional, Enterprise, Performance, Unlimited, and Developer editions.