PyTorch Lightning

PyTorch Lightning supports pretraining and fine tuning AI models across GPU setups.

github.com/lightning-AI/lightning
PyTorch Lightning homepage screenshot

About PyTorch Lightning

PyTorch Lightning is a deep learning framework for pretraining and fine-tuning AI models with PyTorch. It organizes PyTorch code to automate infrastructure work such as backpropagation, mixed precision, and multi-GPU and distributed training, while leaving model logic under user control and scaling from CPU to multi-node GPUs without changing core code.

It offers two packages, PyTorch Lightning for training and deployment at scale and Lightning Fabric for expert-level control. It can run on user hardware or cloud infrastructure, or through Lightning Cloud, and references LitServe for building inference servers in Python.

Key features

  • Automate backpropagation, mixed precision and distributed training setup
  • Scale training from CPU to multi-node GPUs without changing core code
  • Define models with LightningModule for training and inference logic
  • Choose abstraction level via Lightning and Fabric packages
  • Run on own hardware, cloud, or Lightning Cloud service
  • Build custom inference servers in Python with LitServe
Best for: PyTorch users who want to pretrain and fine-tune models without maintaining distributed training code.
Good for
  • Open-source codebase for PyTorch training infrastructure
  • Automates repetitive engineering code while keeping model logic control
  • Runs on own hardware, cloud infrastructure, or Lightning Cloud

PyTorch Lightning at a glance

Type
Open-source project
Pricing
Not confirmed. Check the site
Open source
Yes · Source code
Language
English
Last checked
Oct 5, 2026 · Online when checked
Listed
Oct 5, 2026

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PyTorch Lightning FAQ

How do I install Lightning?
Install with pip install lightning, or with conda using conda install lightning -c conda-forge. Optional dependencies and source installs are also documented.
What are the two core packages?
PyTorch Lightning for training and deploying PyTorch at scale, and Lightning Fabric for expert-level control with less abstraction.
Can I run it without managing my own infrastructure?
Yes. You can run on your own hardware or cloud, or use Lightning Cloud to access GPUs, autoscaling, and monitoring.
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