How Can I create custom colliders in unity

Unity Engine
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1

So I wanna create a custom collider in unity but how can I do That.
I’ve looked at Unity’s collider class and it doesn’t have anything to override the colliders Behaviour.

2

You don’t specify 2D or 3D physics. You say “custom collider” which seems to indicate geometry but then you mention overriding behaviour so I would suggest you clarify what you really need with some more detail.