Flux: The Julia Machine Learning Library

Flux is a library for machine learning geared towards high-performance production pipelines. It comes "batteries-included" with many useful tools built in, but also lets you use the full power of the Julia language where you need it. We follow a few key principles:

  • Doing the obvious thing. Flux has relatively few explicit APIs for features like regularisation or embeddings. Instead, writing down the mathematical form will work – and be fast.
  • Extensible by default. Flux is written to be highly extensible and flexible while being performant. Extending Flux is as simple as using your own code as part of the model you want - it is all high-level Julia code. When in doubt, it’s well worth looking at the source. If you need something different, you can easily roll your own.
  • Performance is key. Flux integrates with high-performance AD tools such as Zygote.jl for generating fast code. Flux optimizes both CPU and GPU performance. Scaling workloads easily to multiple GPUs can be done with the help of Julia's GPU tooling and projects like DaggerFlux.jl.
  • Play nicely with others. Flux works well with Julia libraries from data frames and images to differential equation solvers, so you can easily build complex data processing pipelines that integrate Flux models.


Download Julia 1.6 or later, if you haven't already. You can add Flux using Julia's package manager, by typing ] add Flux in the Julia prompt.

If you have CUDA you can also run ] add CUDA to get GPU support; see here for more details.

NOTE: Flux used to have a CuArrays.jl dependency until v0.10.4, replaced by CUDA.jl in v0.11.0. If you're upgrading Flux from v0.10.4 or a lower version, you may need to remove CuArrays (run ] rm CuArrays) before you can upgrade.

Learning Flux

There are several different ways to learn Flux. If you just want to get started writing models, the model zoo gives good starting points for many common ones. This documentation provides a reference to all of Flux's APIs, as well as a from-scratch introduction to Flux's take on models and how they work. Once you understand these docs, congratulations, you also understand Flux's source code, which is intended to be concise, legible and a good reference for more advanced concepts.


All Flux users are welcome to join our community on the Julia forum, or the slack (channel #machine-learning). If you have questions or issues we'll try to help you out.

If you're interested in hacking on Flux, the source code is open and easy to understand – it's all just the same Julia code you work with normally. You might be interested in our intro issues to get started or our contributing guide.