The low-level virtual machine (llvm) is a collection of libraries and tools that make it easy to build compilers, optimizers, just-in-time code generators, and many other compiler-related programs. llvm uses a single, language-independent virtual instruction set both as an offline code representation (to communicate code between compiler phases and to run-time systems) and as the compiler internal representation (to analyze and transform programs). this persistent code representation allows a common set of sophisticated compiler techniques to be applied at compile-time, link-time, install-time, run-time, or "idle-time" (between program runs).

the strengths of the llvm infrastructure are its extremely simple design (which makes it easy to understand and use), source-language independence, powerful mid-level optimizer, automated compiler debugging support, extensibility, and its stability and reliability. llvm is currently being used to host a wide variety of academic research projects and commercial projects. llvm includes c and c++ front-ends, a front-end for a forth-like language (stacker), a young scheme front-end, and java support is in development. llvm can generate code for x86, sparcv9, powerpc, or it can emit c code.

llvm is the key component of the clang compiler and the gcc plugin called dragonegg.