Board Thread:The Flash discussions/@comment-4300738-20171109194922/@comment-4300738-20171111184808

It is canon in a sense. It is set in an alternate timeline where Barry never created Flashpoint.

The prolouge is the ending scene from S2E23 ("The Race of His Life") with Barry and Iris on the doorstep; although Barry reconsiders seconds before he would have gone back in time.