What is the difference between a build frontend and a build backend?

The frontend is the tool you run (uv, pip, `python -m build`). The backend is the library the frontend invokes to do the actual work of producing wheels and sdists (setuptools, hatchling, flit_core, uv_build). Any PEP 517-compliant frontend can invoke any compliant backend without special-case wiring.

Which build frontend should I use?

Use `uv build` for uv projects. For non-uv projects, `python -m build` from PyPA is the dedicated standalone build tool. pip also acts as a frontend when installing a package from source, but it is not designed as a standalone build command.

Why does a build frontend use an isolated environment?

The build backend and its plugins must be installed before the build runs, but they should not pollute the project's virtual environment. By default, the frontend creates a temporary environment, installs only what the backend requires, runs the build, and discards it. This separates build-time and runtime dependencies.

What is a build frontend?

Q: What is a build frontend?

A build frontend is the command-line tool a developer runs to produce Python packages. It typically creates an isolated environment, installs the build backend there, and calls standardized hook functions to produce wheels and sdists. Common build frontends are uv (via `uv build`), PyPA's build (via `python -m build`), and pip when it builds a package from source.

by Tim Hopper · Markdown

Packaging

A build frontend is a tool that invokes build backends to create Python packages. It typically creates an isolated environment for the build and delegates the work of producing artifacts to the backend.

Which build frontends are there?

pip: the default package installer; acts as a build frontend when installing a package from source with no matching wheel
build: PyPA’s dedicated PEP 517 build tool, designed specifically for producing packages
uv: acts as a build frontend via uv build
poetry, hatch, pdm: project management tools with build capabilities

What does a build frontend do?

When you run a build command, the frontend reads the [build-system] table in pyproject.toml to find the declared backend and its build requirements. It then typically creates an isolated environment, installs those requirements there, and calls the backend’s hook functions to produce wheels and sdists.

Note

Build backends implement PEP 517’s standardized hook API, and frontends call those hooks through it. Any compliant frontend can invoke any compliant backend.

Run a build

Using the build frontend:

python -m build .             # Build both wheel and sdist
python -m build --wheel .     # Build only wheel
python -m build --sdist .     # Build only sdist

Using uv as a build frontend:

uv build                      # Build both formats
uv build --sdist             # Build only sdist
uv build --wheel             # Build only wheel

Learn More

What is a build backend? explains the tool that does the actual build work
What is PEP 517? covers the standard that defined the frontend-backend interface
build reference documents PyPA’s dedicated build frontend
uv reference covers uv build and other uv commands

Last updated on July 16, 2026

What is a build backend?What is a Dependency Cooldown?

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