QBE, a compact compiler backend developed by Quentin Carbonneaux, is a lightweight alternative to larger compiler backends such as LLVM and GCC. Designed to be small enough for a single developer to understand, QBE uses a static single-assignment (SSA) intermediate representation (IR), supports the C ABI, and serves as the backend for projects such as Hare and the cproc C11 compiler. Frontends emit the textual form of QBE's IR directly; QBE then takes care of register allocation, optimization, and native-code generation, producing assembly for the target architecture.