# PyTorch 2.15 makes the rewritten NCCL backend the default

> Original title: PyTorch 2.15 Release Blog

- Source: PyTorch Blog
- Published: 2026-10-28T17:44:20.000Z
- Bad Influence: https://badinfluence.news/items/sxl9pt5r1c42i6lj959xp0e0j
- Original: https://pytorch.org/blog/pytorch-2-15-release-blog/

## Summary

PyTorch 2.15 is released with a rewritten NCCL backend that is now the default for every nccl process group, with TORCH_DIST_USE_NCCL2=0 and nccl-legacy as rollback paths. The release also adds a flight recorder that dumps on hangs, FSDP2 precision and CUDA graph controls, and FP8 and decode speedups on Apple Silicon. Python 3.10 and macOS 14 support are dropped, and the default CUDA wheel moves to 13.2.

## Why it matters

The release notes list concrete default changes, rollback paths, and deprecations, which matter for teams running distributed training or Apple Silicon inference.