Redexer is a reengineering tool designed for manipulating Android application binaries through DEX file analysis and modification. The tool parses DEX files into in-memory data structures, enabling detailed examination of Android app binaries. It includes RefineDroid functionality that infers parameters used by applications when accessing specific permissions. Redexer provides Dr. Android capabilities, which stands for Dalvik Rewriting for Android, allowing users to modify and unparse data structures to generate output DEX files. This enables binary manipulation and reengineering of Android applications. The tool requires OCaml and Ruby environments for operation, along with OCaml SHA library for handling SHA-1 signatures in DEX format. Installation is facilitated through OPAM package manager for managing dependencies. Redexer supports security research and analysis of Android applications by providing low-level access to DEX file structures and permission usage patterns.