For 3.14, from October 2025, free-threaded Python was "much safer" and "much faster" with a 0-10% slowdown for single-threaded workloads. "I'm still personally shocked that we got to 0% slowdown, that's on Arm hardware, there's some magic going on there, I don't know what it is, but it's amazing." On Linux using GCC, it's usually around 5%, though it can go up to 10%, particularly with older compilers.

That's interesting about the Arm hardware. I hadn't noticed any slowdown on the Mac with my own primitive benchmarks, but the newer Macs all use Arm so that makes sense.