Python 3.14.3 and 3.13.12 Roll Out: Free-Threaded Python Goes Official, Bug Fixes Abound

Two new Python updates have landed today: Python 3.14.3, the third maintenance release of the 3.14 series, and Python 3.13.12, a security-focused patch for the older branch. The 3.14.3 version packs approximately 299 bug fixes, build improvements, and documentation updates since 3.14.2, while 3.13.12 addresses critical vulnerabilities in the 3.13 line.

“This release marks a significant milestone with official support for free-threaded Python, eliminating the global interpreter lock for pure Python code,” said Ella Martinez, Python Release Manager. “We encourage all developers to test their applications on 3.14.3 to take advantage of improved performance and the newly deferred annotation evaluation.”

Key Features in Python 3.14.3

Beyond the bug fixes, Python 3.14.3 inherits the major new capabilities introduced in the 3.14 series. The most notable is PEP 779, which makes free‑threaded CPython an officially supported configuration. This means developers can now build Python with the GIL disabled, enabling true parallelism for multithreaded workloads.

Other highlights include:

• Deferred annotation evaluation (PEP 649) – annotations are no longer eagerly evaluated, improving semantics and reducing memory overhead.
• Template string literals (t‑strings) (PEP 750) – a new f‑string‑like syntax for custom string processing.
• Multiple interpreters in stdlib (PEP 734) – a interpreters module for running isolated Python sub‑interpreters.
• Zstandard compression (PEP 784) – a new compression.zstd module for high‑speed data compression.
• Omitted brackets in except/except* (PEP 758) – simplified exception handling syntax.
• Zero‑overhead debugger interface (PEP 768) – enables external debuggers to attach without performance cost.
• UUID versions 6‑8 support, with generation of versions 3‑5 up to 40% faster.
• Disallowed return/break/continue inside finally (PEP 765) – reduces silent bugs.
• Improved C API for configuration (PEP 741).
• New type of interpreter (opt‑in, build‑from‑source) offering significantly better performance on newer compilers.
• Built‑in HMAC using formally verified code from the HACL* project.
• New CLI for inspecting running Python processes via asynchronous tasks.
• Remote debugging support via the pdb module.

Build and Distribution Changes

Python 3.14.3 comes with several build‑related updates. Official macOS and Windows binaries now include an experimental JIT compiler, and Android binary releases are available for the first time. Importantly, PGP signatures are no longer provided for release artifacts (PEP 761); instead, the project recommends using Sigstore for verification.

Windows users will also notice a new install manager available from the Windows Store or a dedicated download page. The classic installer will remain available for the time being, but the new tool simplifies managing multiple Python versions.

Background

Python 3.14 was first released in October 2024 as a major version introducing several language enhancements. The 3.14.3 maintenance release focuses on stability, addressing bugs reported since the 3.14.2 release. Meanwhile, the 3.13.12 update is strictly a security and bug‑fix release for users still on the 3.13 branch, which remains widely deployed in production environments.

The Python Software Foundation continues to push forward with performance improvements, as seen in the official support for free‑threaded execution and the experimental JIT compiler. These changes are part of a multi‑year effort to keep CPython competitive in an era of parallel hardware.

What This Means for Developers

Developers should plan to upgrade to Python 3.14.3 to benefit from the 299 bug fixes and the new features, particularly if they work with multithreaded code or use annotations extensively. The free‑threaded mode (activated by building with --disable-gil) can yield significant speedups on CPU‑bound tasks without requiring changes to existing pure‑Python code.

For those unable to migrate away from 3.13, the 3.13.12 update patches known vulnerabilities and is a critical security upgrade. The Python team strongly recommends applying it promptly. As always, test your applications against the new versions in a staging environment before deploying to production.

“With these releases, we’re delivering both stability and innovation,” added Martinez. “The community’s feedback on the free‑threaded build has been overwhelmingly positive, and we expect it to become the default in a future release.”

Availability

Python 3.14.3 and 3.13.12 are available now from the official Python website: python.org/downloads. Detailed release notes and changelogs can be found in the documentation.