JIT compiler

A just-in-time (JIT) compiler is a part of the runtime environment for Python that compiles bytecode into machine code at runtime. This approach contrasts with traditional ahead-of-time (AOT) compilation, which compiles the entire program before execution.

In CPython, the JIT compiler introduced in Python 3.13 through PEP 744 is still experimental and is disabled by default. Since Python 3.14, the official Windows and macOS installers include it, or you can build CPython from source with the --enable-experimental-jit option.

By compiling code just in time, a JIT compiler can optimize the execution of your program based on the actual runtime context, potentially improving performance significantly.

A person points at a monitor showing a rising performance line chart, beside a machine with a 3.15 flip-counter, a JIT compiling screen, a Python logo, and Trace and Register panels.

Tutorial

Python 3.15 Preview: Upgraded JIT Compiler

Learn how the upgraded Python 3.15 JIT compiler speeds up your code with a new tracing frontend, register allocation, and in-place numeric operations.

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For additional information on related topics, take a look at the following resources:

By Leodanis Pozo Ramos • Updated July 7, 2026
Python Glossary Share Feedback