bytecode

Bytecode is a form of low-level code designed to be executed by a software virtual machine or interpreter rather than directly by a computer’s processor. It is an intermediate representation created by compiling a high-level language to an instruction set that abstracts away hardware details. The same bytecode can typically run on different architectures if an appropriate virtual machine is available.

Bytecode is usually executed by a virtual machine, which may interpret instructions, translate them just-in-time into native code, or perform multiple levels of translation. This model provides portability and safety, as the VM can enforce boundaries such as memory access and sandboxing. Bytecode formats are often compact and amenable to ahead-of-time analysis, verification, and optimization.

Examples include Java bytecode for the Java Virtual Machine, Python bytecode used by CPython and other implementations, and the Common Intermediate Language (CIL) used by the .NET runtime. WebAssembly, while designed for the web, is commonly described as a binary bytecode for a stack-based VM. Other languages also target their own VM bytecodes.

Bytecode trades some raw performance for portability and security. Modern runtimes employ just-in-time compilation or whole-program optimization to approach native-speed execution, while startup time and VM overhead remain considerations. Bytecode remains a core technology for managed runtimes, scripting languages, and cross-platform software distribution.