Critical Updates

This release includes updates that improve the performance, logic, and usability of Salesforce but might affect your existing customizations.

To ensure a smooth transition, each critical update has an opt-in period, which ends on the auto-activation date that’s displayed on the Critical Updates page in Setup. During this period, you can manually activate and deactivate the update as often as you need to evaluate the impact on your organization and modify affected customizations. After the opt-in period has passed, the update is automatically activated. For more details, see Critical Updates Overview.

Enable My Domain to Use Lightning Components
For security purposes, Lightning components now require you to define a custom Salesforce domain name for your organization. If you’re using Lightning components today, you might need to take action to avoid having Lightning components-based customizations disabled when Winter ’16 is released.
PageReference getContent() and getContentAsPDF() Methods Behave as Callouts” Critical Update Postponed
In Summer ’15 we made a change to the behavior of the getContent() and getContentAsPDF() methods of the PageReference object. This change was released as a critical update named “PageReference getContent() and getContentAsPDF() Methods Behave as Callouts” and was scheduled for auto-activation in Winter ’16. The auto-activation date has been postponed until Spring ’16.
Serve Static Resources from the Visualforce Domain” Critical Update Postponed
In Summer ’15 we made a change to the domain from which static resources are served. This change was released as a critical update named “Serve Static Resources from the Visualforce Domain” and was scheduled for auto-activation in Winter ’16. The auto-activation date has been postponed until Spring ’16.