Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The read-only originalTarget property of the Event interface returns the original target of the event before any retargetings. Unlike Event.explicitOriginalTarget it can also be native anonymous content.
See also Comparison of Event Targets
