Providing synchronization of data between application instances that execute script, and in preferred embodiments, without the use of synchronization primitives in the script and without the ability to reschedule events in at least one of the instances. Blocking code is provided in the application instances that is adapted for checking a flag to be set by the other component. One component can thereby inform the other component when it is ready to receive data, and the other component can inform the one component when the other component is finished with the data. In one scenario, the provided synchronization enables a browser instance that is terminating to safely provide its data to a separate browser instance, and enables the separate browser instance to know when the provided data can safely be manipulated.