When you are standing on the block next to the worldborder, and you shrink the border at least 4 blocks, you will be outside it, and free to roam around. If you are in survival, it will start killing you after a certain distance, but if you are in creative, have fun exploring!
MC-69317
World border ineffective after shrinking past where you are.
Resolved
Works As Intended
0
Intended, so that players are free to get back inside the border if that happens.