LuaJIT

LuaJIT is a Just-In-Time compiler and runtime for the Lua programming language. It was created by Mike Pall and first released in 2009 with the aim of delivering a high-performance implementation of Lua that could rival native code execution. LuaJIT emphasizes speed while preserving the familiar Lua 5.1 semantics.

The core of LuaJIT is a tracing JIT compiler. It records frequently executed paths (traces) during execution and compiles them to native machine code, applying aggressive optimizations to the hot paths. This approach typically yields substantial speedups for tight loops and compute-intensive Lua workloads, while the interpreter remains available for non-JIT code paths.

Key features include the LuaJIT FFI (foreign function interface), which allows calling C functions and manipulating C data structures directly from Lua without glue code. This capability greatly simplifies integration with C libraries and is a major factor in LuaJIT’s popularity. LuaJIT also provides tight integration with Lua’s garbage collector and standard libraries, contributing to overall performance and developer ergonomics.

Compatibility and limitations: LuaJIT implements most of Lua 5.1 APIs and language features but does not fully support Lua 5.2 and later additions. Some Lua 5.2+/Lua 5.3 features may require workarounds. LuaJIT is primarily single-threaded; multiple threads can be used by running separate Lua states, but the JIT compiler itself is not designed for concurrent code generation.

Platform support: LuaJIT runs on major operating systems including Linux, Windows, macOS, and BSD variants, on architectures such as x86, x86-64, ARM, and ARM64.

License and status: LuaJIT is released under a permissive MIT-style license. Development has slowed since the mid-2010s, with no canonical new official releases; however, forks and community use remain common, notably in projects like OpenResty and other high-performance Lua deployments.