DIFTS (Design and Implementation of Formal Tools and Systems) workshop emphasizes insightful experiences in formal tools and systems design. The first DIFTS workshop was held in 2011, DIFTS11. It provides a forum for sharing challenges and solutions that are original with ground breaking results. Often the design and implementation of tools for formal analysis require non-trivial engineering decisions. Many challenges are faced, which often can only be met with ingenious implementation techniques. These techniques actually play a crucial role in making the idea work in practice. The workshop provides an opportunity for discussing engineering aspects and various design decisions required to put such formal tools and systems in practical use. DIFTS takes a broad view of the formal tools/systems area, and solicits contributions from domains including, but not restricted to, decision procedures verification testing validation diagnosis debugging synthesis