This is something that many others are reporting as well. I just tell them all to reduce the size of the box collider if it’s hindering their game play. Have not yet confirmed if this is a bug or by design.
Not sure if this is the same issue, but something similar was happening to me. I was using a sprite as a prefab for platforms, but the box colliders were larger than my sprite. I read somewhere that 1 unity in unity is 100 pixels. I resized my image accordingly and it ended up being a snug fit.
This is not a bug, it’s part of the way Box2D works. Box2D implements a “skin” around polygons/edges (this means “box” as well which is just a polygon).
You can read about it in the Box2D manual and FAQ here:
Sorry for bumping up this old thread, but I’m having some issues when setting up the Box Collider 2D for bodies of 1x1 pixels size.
The objects are debris that should interact with the physics world but they stack on top of each other with a gap when using a box as collider, for circles they work just fine.
What would you recommend me to do in order to reduce this gap between the debris? any help or comment is appreciated.