Radare2 is a modular reverse engineering framework written in C. It provides a comprehensive set of libraries and command-line tools for binary analysis, disassembly, debugging, emulation, and file format parsing. The architecture is plugin-based: every major subsystem (architectures, binary formats, I/O backends, debuggers, filesystems, crypto, scripting languages) is implemented as a plugin registered via a common RLibStruct pattern. The core library (libr/) contains reusable data structures (RBTrees, RBuffer, RStrBuf, RList, etc.), utilities (base64, ASN.1, regex, event system, thread wrappers), and analysis engines (ESIL emulator, search algorithms, type propagation). The framework supports dozens of CPU architectures (x86, ARM, MIPS, RISC-V, etc.) and binary formats (ELF, PE, Mach-O, DEX, etc.), and can be extended via language bindings (JavaScript, Python, Rust, etc.) and a package manager (r2pm). Despite its large codebase and some legacy components, the project is actively maintained with continuous integration, fuzz testing, and a responsive issue tracker.