How uv got so fast

uv installs packages faster than pip by an order of magnitude. The usual explanation is “it’s written in Rust.” That’s true, but it doesn’t explain much. Plenty of tools are written in Rust without being notably fast. The interesting question is what design decisions made the difference. Charlie Marsh’s Jane Street talk and a Xebia engineering deep-dive do an excellent job at covering the technical details. Let’s dig into the design decisions that led to it: standards that enable fast paths, things uv drops that pip supports, and optimizations that don’t require Rust at all. The standards that made uv possible pip’s slowness isn’t a failure of implementation. For years, Python packaging required executing code to find out what a package needed. The problem was setup.py . You couldn’t know a package’s dependencies without running its setup script. But you couldn’t run its setup script without installing its build dependencies. PEP 518 in 2016 called this out explicitly: “You can’t execute a setup.py file without knowing its dependencies, but currently there is no standard way to know what those dependencies are in an automated fashion without executing the setup.py file.” This chicken-and-egg problem forced pip to download packages, execute untrusted code, fail, install missing build tools, and try again. Every install was potentially a cascade of subprocess spawns and arbitrary code execution. Installing a source distribution was essentially curl | bash with extra steps. The fix came in stages: PEP 518 (2016) created pyproject.toml, giving packages a place to declare build dependencies without code execution. The TOML format was borrowed from Rust’s Cargo, which makes a Rust tool returning to fix Python packaging feel less like coincidence. PEP 517 (2017) separated build frontends from backends, so pip didn’t need to understand setuptools internals. PEP 621 (2020) standardized the [project] table, so dependencies could be read by parsing TOML rather than running Python. PEP 658 (2022) put package metadata directly in the Simple Repository API, so resolvers could fetch dependency information without downloading wheels at all. PEP 658 went live on PyPI in May 2023. uv launched in February 2024. The timing isn’t coincidental. uv could be fast because the ecosystem finally had the infrastructure to support it. A tool like uv couldn’t have shipped in 2020. The standards weren’t there yet. Other ecosystems figured this out earlier. Cargo has had static metadata from the start. npm’s package.json is declarative. Python’s packaging standards finally bring it to parity. What uv drops Speed comes from elimination. Every code path you don’t have is a code path you don’t wait for. uv’s compatibility documentation is a list of things it doesn’t do: No .egg support. Eggs were the pre-wheel binary format. pip still handles them; uv doesn’t even try. The format has been obsolete for over a decade. No pip.conf. uv ignores pip’s configuration files entirely. No parsing, no environment variable lookups, no inheritance from system-wide and per-user locations. No bytecode compilation by default. pip compiles .py files to .pyc during installation. uv...

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