Python 3.13 Free-Threaded Mode: Real-World Performance Benchmarks for 2026
Python 3.13 ships an experimental free-threaded build that finally removes the GIL. The marketing is exciting; the reality is more nuanced. We benchmarked free-threaded Python on a representative range of workloads β CPU-bound, I/O-bound, mixed β and measured the single-threaded slowdown that nobody talks about. Here is what to actually expect in 2026, and when free-threaded mode is ready for production use....