“Epistemic safety” refers to an epistemic status in which the subject acquires true beliefs without involving epistemic luck. There is a tradition of cashing out safety-defining modality in terms of possible world semantics (as put forward by Duncan Pritchard), and even Julian Dutant's and Martin Smith's normalcy-based notions of safety also take this semantics as a significant component of them. However, such an approach has to largely depend on epistemologists’ ad hoc intuitions on how to individuate possible worlds and how to pick out “close” worlds. In contrast, I propose a probabilistic approach to safety to maximally preclude the preceding type of ad hoc-ness. The main idea is as follows: Each epistemic vignette wherein a subject S holds a true belief p has to be evaluated by a safety-ascriber, hence, S holds a true belief p safely iff according to the safety-ascriber's evaluation (which is based on her background knowledge), the probability of the occurrence of the truth-maker of p is above a pre-fixed “safety threshold”. My theory will be applied to Lottery Cases, Gettierized Cases and Skeptical Cases to test the scope of its applicability.