How to remove a leaking jar of Kraft Marshmallow Creme from a cabinet shelf?

Hot water may help to soften it, depending on how long it's been sitting.

While I recognize your concern about the jar potentially breaking, if you can soften the creme that leaked, you can use a butter knife or similar flat object to GENTLY work your way around, prying up by rocking the knife left to right. Obviously getting to the back of the shelf isn't going to be possible, but with some time and effort, you should be able to loosen the jar enough you can continue to apply hot water underneath as you go, and it should loosen the back of the jar. It's likely that the goo on the bottom of the jar is not nearly as solid, because it hasn't had the airflow to it that the outside has had; alternately, if you don't feel like using hot water, try chipping away at the hardened mess - obviously going to take longer, but may be better for the wood if it's not sealed.

I would spray the area with HOT water and take a butter knife dipped in hot water and try to slide it under the jar. Hope it helps. Good Luck.

hot hot water, soap and some elbow grease. Marshmallows are only sugar and will dissolve in water eventually.

Try using a blow dryer to loosen it. Good Luck!

neither of the above haha what your need is lemon juice. the natural acids will help.