Why did uv originally use Hatch as a build backend?

When uv first launched, it didn’t implement its own build backend for creating Python packages. Instead, it used existing backends when packaging projects.

Running uv init with the --package flag originally set up Hatchling (hatch’s build backend) as the default backend in the generated pyproject.toml:

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

This was purely a configuration choice: uv needed to select some backend for packaged projects, and Hatchling provided a modern, standards-compliant option with minimal dependencies. Now that uv_build is the default, new projects use uv’s own backend, but the rationale for choosing Hatchling originally still explains why so many existing uv projects use it.