# uv

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An extremely fast Python package installer and resolver, written in Rust. Designed as a drop-in
replacement for common `pip` and `pip-tools` workflows.

uv is backed by [Astral](https://astral.sh), the creators of [Ruff](https://github.com/astral-sh/ruff).

## Highlights

- ⚖️ Drop-in replacement for common `pip`, `pip-tools`, and `virtualenv` commands.
- ⚡️ [10-100x faster](https://github.com/astral-sh/uv/blob/main/BENCHMARKS.md) than `pip`
  and `pip-tools` (`pip-compile` and `pip-sync`).
- 💾 Disk-space efficient, with a global cache for dependency deduplication.
- 🐍 Installable via `curl`, `pip`, `pipx`, etc. uv is a static binary that can be installed
  without Rust or Python.
- 🧪 Tested at-scale against the top 10,000 PyPI packages.
- 🖥️ Support for macOS, Linux, and Windows.
- 🧰 Advanced features such as [dependency version overrides](#dependency-overrides) and
   [alternative resolution strategies](#resolution-strategy).
- ⁉️ Best-in-class error messages with a conflict-tracking resolver.
- 🤝 Support for a wide range of advanced `pip` features, including editable installs, Git
  dependencies, direct URL dependencies, local dependencies, constraints, source distributions,
  HTML and JSON indexes, and more.

## Getting Started

Install uv with our standalone installers, or from [PyPI](https://pypi.org/project/uv/):

```shell
# On macOS and Linux.
curl -LsSf https://astral.sh/uv/install.sh | sh

# On Windows.
powershell -c "irm https://astral.sh/uv/install.ps1 | iex"

# With pip.
pip install uv

# With pipx.
pipx install uv

# With Homebrew.
brew install uv

# With Pacman.
pacman -S uv
```

To create a virtual environment:

```shell
uv venv  # Create a virtual environment at .venv.
```

To activate the virtual environment:

```shell
# On macOS and Linux.
source .venv/bin/activate

# On Windows.
.venv\Scripts\activate
```

To install a package into the virtual environment:

```shell
uv pip install flask                # Install Flask.
uv pip install -r requirements.txt  # Install from a requirements.txt file.
uv pip install -e .                 # Install the current project in editable mode.
uv pip install "package @ ."        # Install the current project from disk.
uv pip install "flask[dotenv]"      # Install Flask with "dotenv" extra.
```

To generate a set of locked dependencies:

```shell
uv pip compile pyproject.toml -o requirements.txt   # Read a pyproject.toml file.
uv pip compile requirements.in -o requirements.txt  # Read a requirements.in file.
echo flask | uv pip compile - -o requirements.txt  # Read from stdin.
uv pip freeze | uv pip compile - -o requirements.txt  # Lock the current environment.
```

To sync a set of locked dependencies with the virtual environment:

```shell
uv pip sync requirements.txt  # Install from a requirements.txt file.
```

uv's `pip-install` and `pip-compile` commands support many of the same command-line arguments
as existing tools, including `-r requirements.txt`, `-c constraints.txt`, `-e .` (for editable
installs), `--index-url`, and more.

## Limitations

While uv supports a large subset of the `pip` interface, it does not support the entire feature set.
In some cases, those differences are intentional; in others, they're a result of uv's early stage of
development.

For details, see our [`pip` compatibility guide](./PIP_COMPATIBILITY.md).

Like `pip-compile`, uv generates a platform-specific `requirements.txt` file (unlike, e.g.,
`poetry` and `pdm`, which generate platform-agnostic `poetry.lock` and `pdm.lock` files). As such,
uv's `requirements.txt` files may not be portable across platforms and Python versions.

## Roadmap

uv is an extremely fast Python package resolver and installer, designed as a drop-in
replacement for `pip`, `pip-tools` (`pip-compile` and `pip-sync`), and `virtualenv`.

uv represents an intermediary goal in our pursuit of a ["Cargo for Python"](https://blog.rust-lang.org/2016/05/05/cargo-pillars.html#pillars-of-cargo):
a comprehensive project and package manager that is extremely fast, reliable, and easy to use.

Think: a single binary that bootstraps your Python installation and gives you everything you need to
be productive with Python, bundling not only `pip`, `pip-tools`, and `virtualenv`, but also `pipx`,
`tox`, `poetry`, `pyenv`, `ruff`, and more.

Our goal is to evolve uv into such a tool.

In the meantime, though, the narrower `pip-tools` scope allows us to solve the low-level problems
involved in building such a tool (like package installation) while shipping something immediately
useful with a minimal barrier to adoption.

## Advanced Usage

### Python discovery

uv itself does not depend on Python, but it does need to locate a Python environment to (1)
install dependencies into the environment and (2) build source distributions.

When running `pip sync` or `pip install`, uv will search for a virtual environment in the
following order:

- An activated virtual environment based on the `VIRTUAL_ENV` environment variable.
- An activated Conda environment based on the `CONDA_PREFIX` environment variable.
- A virtual environment at `.venv` in the current directory, or in the nearest parent directory.

If no virtual environment is found, uv will prompt the user to create one in the current
directory via `uv venv`.

When running `pip compile`, uv does not _require_ a virtual environment and will search for a
Python interpreter in the following order:

- An activated virtual environment based on the `VIRTUAL_ENV` environment variable.
- An activated Conda environment based on the `CONDA_PREFIX` environment variable.
- A virtual environment at `.venv` in the current directory, or in the nearest parent directory.
- The Python interpreter available as `python3` on macOS and Linux, or `python.exe` on Windows.

If a `--python-version` is provided to `pip compile` (e.g., `--python-version=3.7`), uv will
search for a Python interpreter matching that version in the following order:

- An activated virtual environment based on the `VIRTUAL_ENV` environment variable.
- An activated Conda environment based on the `CONDA_PREFIX` environment variable.
- A virtual environment at `.venv` in the current directory, or in the nearest parent directory.
- The Python interpreter available as, e.g., `python3.7` on macOS and Linux.
- The Python interpreter available as `python3` on macOS and Linux, or `python.exe` on Windows.
- On Windows, the Python interpreter returned by `py --list-paths` that matches the requested
  version.

### Installing into arbitrary Python environments

Since uv has no dependency on Python, it can even install into virtual environments other than
its own. For example, setting `VIRTUAL_ENV=/path/to/venv` will cause uv to install into
`/path/to/venv`, no matter where uv is installed.

uv can also install into arbitrary, even non-virtual environments by providing a `--python` argument
to `uv pip sync` or `uv pip install`. For example, `uv pip install --python=/path/to/python` will
install into the environment linked to the `/path/to/python` interpreter.

For convenience, `uv pip install --system` will install into the system Python environment, as an
approximate shorthand for, e.g., `uv pip install --python=$(which python3)`. Though we generally
recommend the use of virtual environments for dependency management, `--system` is intended to
enable the use of uv in continuous integration and containerized environments.

Installing into system Python across platforms and distributions is notoriously difficult. uv
supports the common cases, but will not work in all cases. For example, installing into system
Python on Debian prior to Python 3.10 is unsupported due to the [distribution's patching
of `distutils` (but not `sysconfig`)](https://ffy00.github.io/blog/02-python-debian-and-the-install-locations/).
While we always recommend the use of virtual environments, uv considers them to be required in
these non-standard environments.

### Git authentication

uv allows packages to be installed from Git and supports the following schemes for authenticating with private
repositories.

Using SSH:

- `git+ssh://git@<hostname>/...` (e.g. `git+ssh://git@github.com/astral-sh/uv`)
- `git+ssh://git@<host>/...` (e.g. `git+ssh://git@github.com-key-2/astral-sh/uv`)

See the [GitHub SSH documentation](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/about-ssh) for more details on how to configure SSH.

Using a password or token:

- `git+https://<user>:<token>@<hostname>/...` (e.g. `git+https://git:github_pat_asdf@github.com/astral-sh/uv`)
- `git+https://<token>@<hostname>/...` (e.g. `git+https://github_pat_asdf@github.com/astral-sh/uv`)
- `git+https://<user>@<hostname>/...` (e.g. `git+https://git@github.com/astral-sh/uv`)

When using a GitHub personal access token, the username is arbitrary. GitHub does not support logging in with password directly, although other hosts may. If a username is provided without credentials, you will be prompted to enter them.

If there are no credentials present in the URL and authentication is needed, the [Git credential helper](https://git-scm.com/doc/credential-helpers) will be queried.

### HTTP authentication

uv supports credentials over HTTP when querying package registries.

Authentication can come from the following sources, in order of precedence:

- The URL, e.g., `https://<user>:<password>@<hostname>/...`
- A [`netrc`](https://everything.curl.dev/usingcurl/netrc) configuration file
- A [keyring](https://github.com/jaraco/keyring) provider (requires opt-in)

If authentication is found for a single net location (scheme, host, and port), it will be cached for the duration
of the command and used for other queries to that net location. Authentication is not cached across invocations of
uv.

Note `--keyring-provider subprocess` or `UV_KEYRING_PROVIDER=subprocess` must be provided to enable keyring-based
authentication.

Authentication may be used for hosts specified in the following contexts:

- `index-url`
- `extra-index-url`
- `find-links`
- `package @ https://...`

See the [`pip` compatibility guide](PIP_COMPATIBILITY.md#registry-authentication) for details on differences from
`pip`.

### Dependency caching

uv uses aggressive caching to avoid re-downloading (and re-building dependencies) that have
already been accessed in prior runs.

The specifics of uv's caching semantics vary based on the nature of the dependency:

- **For registry dependencies** (like those downloaded from PyPI), uv respects HTTP caching headers.
- **For direct URL dependencies**, uv respects HTTP caching headers, and also caches based on
  the URL itself.
- **For Git dependencies**, uv caches based on the fully-resolved Git commit hash. As such,
  `uv pip compile` will pin Git dependencies to a specific commit hash when writing the resolved
  dependency set.
- **For local dependencies**, uv caches based on the last-modified time of the `setup.py` or
  `pyproject.toml` file.

If you're running into caching issues, uv includes a few escape hatches:

- To force uv to revalidate cached data for all dependencies, run `uv pip install --refresh ...`.
- To force uv to revalidate cached data for a specific dependency, run, e.g., `uv pip install --refresh-package flask ...`.
- To force uv to ignore existing installed versions, run `uv pip install --reinstall ...`.
- To clear the global cache entirely, run `uv cache clean`.

### Resolution strategy

By default, uv follows the standard Python dependency resolution strategy of preferring the
latest compatible version of each package. For example, `uv pip install flask>=2.0.0` will
install the latest version of Flask (at time of writing: `3.0.0`).

However, uv's resolution strategy can be configured to support alternative workflows. With
`--resolution=lowest`, uv will install the **lowest** compatible versions for all dependencies,
both **direct** and **transitive**. Alternatively, `--resolution=lowest-direct` will opt for the
**lowest** compatible versions for all **direct** dependencies, while using the **latest**
compatible versions for all **transitive** dependencies. This distinction can be particularly useful
for library authors who wish to test against the lowest supported versions of direct dependencies
without restricting the versions of transitive dependencies.

For example, given the following `requirements.in` file:

```text
flask>=2.0.0
```

Running `uv pip compile requirements.in` would produce the following `requirements.txt` file:

```text
# This file was autogenerated by uv via the following command:
#    uv pip compile requirements.in
blinker==1.7.0
    # via flask
click==8.1.7
    # via flask
flask==3.0.0
itsdangerous==2.1.2
    # via flask
jinja2==3.1.2
    # via flask
markupsafe==2.1.3
    # via
    #   jinja2
    #   werkzeug
werkzeug==3.0.1
    # via flask
```

However, `uv pip compile --resolution=lowest requirements.in` would instead produce:

```text
# This file was autogenerated by uv via the following command:
#    uv pip compile requirements.in --resolution=lowest
click==7.1.2
    # via flask
flask==2.0.0
itsdangerous==2.0.0
    # via flask
jinja2==3.0.0
    # via flask
markupsafe==2.0.0
    # via jinja2
werkzeug==2.0.0
    # via flask
```

### Pre-release handling

By default, uv will accept pre-release versions during dependency resolution in two cases:

1. If the package is a direct dependency, and its version markers include a pre-release specifier
   (e.g., `flask>=2.0.0rc1`).
1. If _all_ published versions of a package are pre-releases.

If dependency resolution fails due to a transitive pre-release, uv will prompt the user to
re-run with `--prerelease=allow`, to allow pre-releases for all dependencies.

Alternatively, you can add the transitive dependency to your `requirements.in` file with
pre-release specifier (e.g., `flask>=2.0.0rc1`) to opt in to pre-release support for that specific
dependency.

Pre-releases are [notoriously difficult](https://pubgrub-rs-guide.netlify.app/limitations/prerelease_versions)
to model, and are a frequent source of bugs in other packaging tools. uv's pre-release handling
is _intentionally_ limited and _intentionally_ requires user opt-in for pre-releases, to ensure
correctness.

For more, see ["Pre-release compatibility"](./PIP_COMPATIBILITY.md#pre-release-compatibility)

### Dependency overrides

Historically, `pip` has supported "constraints" (`-c constraints.txt`), which allows users to
narrow the set of acceptable versions for a given package.

uv supports constraints, but also takes this concept further by allowing users to _override_ the
acceptable versions of a package across the dependency tree via overrides (`--override overrides.txt`).

In short, overrides allow the user to lie to the resolver by overriding the declared dependencies
of a package. Overrides are a useful last resort for cases in which the user knows that a
dependency is compatible with a newer version of a package than the package declares, but the
package has not yet been updated to declare that compatibility.

For example, if a transitive dependency declares `pydantic>=1.0,<2.0`, but the user knows that
the package is compatible with `pydantic>=2.0`, the user can override the declared dependency
with `pydantic>=2.0,<3` to allow the resolver to continue.

While constraints are purely _additive_, and thus cannot _expand_ the set of acceptable versions for
a package, overrides _can_ expand the set of acceptable versions for a package, providing an escape
hatch for erroneous upper version bounds.

### Multi-version resolution

uv's `pip-compile` command produces a resolution that's known to be compatible with the
current platform and Python version. Unlike Poetry, PDM, and other package managers, uv does
not yet produce a machine-agnostic lockfile.

However, uv _does_ support resolving for alternate Python versions via the `--python-version`
command line argument. For example, if you're running uv on Python 3.9, but want to resolve for
Python 3.8, you can run `uv pip compile --python-version=3.8 requirements.in` to produce a
Python 3.8-compatible resolution.

### Reproducible resolution

uv supports an `--exclude-newer` option to limit resolution to distributions published before a specific
date, allowing reproduction of installations regardless of new package releases. The date may be specified
as a RFC 3339 timestamp (e.g., `2006-12-02T02:07:43Z`) or UTC date in the same format (e.g., `2006-12-02`).

Note the package index must support the `upload-time` field as specified in [`PEP 700`](https://peps.python.org/pep-0700/).
If the field is not present for a given distribution, the distribution will be treated as unavailable.

To ensure reproducibility, messages for unsatisfiable resolutions will not mention that distributions were excluded
due to the `--exclude-newer` flag — newer distributions will be treated as if they do not exist.

## Platform support

uv has Tier 1 support for the following platforms:

- macOS (Apple Silicon)
- macOS (x86_64)
- Linux (x86_64)
- Windows (x86_64)

uv is continuously built, tested, and developed against its Tier 1 platforms. Inspired by the
Rust project, Tier 1 can be thought of as ["guaranteed to work"](https://doc.rust-lang.org/beta/rustc/platform-support.html).

uv has Tier 2 support (["guaranteed to build"](https://doc.rust-lang.org/beta/rustc/platform-support.html)) for the following platforms:

- Linux (PPC64)
- Linux (PPC64LE)
- Linux (aarch64)
- Linux (armv7)
- Linux (i686)
- Linux (s390x)

uv ships pre-built wheels to [PyPI](https://pypi.org/project/uv/) for its Tier 1 and
Tier 2 platforms. However, while Tier 2 platforms are continuously built, they are not continuously
tested or developed against, and so stability may vary in practice.

Beyond the Tier 1 and Tier 2 platforms, uv is known to build on i686 Windows, and known _not_
to build on aarch64 Windows, but does not consider either platform to be supported at this time.

uv supports and is tested against Python 3.8, 3.9, 3.10, 3.11, and 3.12.

## Environment variables

uv accepts the following command-line arguments as environment variables:

- `UV_INDEX_URL`: Equivalent to the `--index-url` command-line argument. If set, uv will use this
  URL as the base index for searching for packages.
- `UV_EXTRA_INDEX_URL`: Equivalent to the `--extra-index-url` command-line argument. If set, uv
  will use this space-separated list of URLs as additional indexes when searching for packages.
- `UV_CACHE_DIR`: Equivalent to the `--cache-dir` command-line argument. If set, uv will use this
  directory for caching instead of the default cache directory.
- `UV_NO_CACHE`: Equivalent to the `--no-cache` command-line argument. If set, uv will not use the
  cache for any operations.
- `UV_PRERELEASE`: Equivalent to the `--prerelease` command-line argument. If set to `allow`, uv
  will allow pre-release versions for all dependencies.
- `UV_SYSTEM_PYTHON`:  Equivalent to the `--system` command-line argument. If set to `true`, uv
  will use the first Python interpreter found in the system `PATH`.
  WARNING: `UV_SYSTEM_PYTHON=true` is intended for use in continuous integration (CI) environments and
  should be used with caution, as it can modify the system Python installation.
- `UV_NATIVE_TLS`: Equivalent to the `--native-tls` command-line argument. If set to `true`, uv
  will use the system's trust store instead of the bundled `webpki-roots` crate.

In each case, the corresponding command-line argument takes precedence over an environment variable.

In addition, uv respects the following environment variables:

- `SSL_CERT_FILE`: If set, uv will use this file as the certificate bundle instead of the system's
  trust store.
- `RUST_LOG`: If set, uv will use this value as the log level for its `--verbose` output. Accepts
  any filter compatible with the `tracing_subscriber` crate. For example, `RUST_LOG=trace` will
  enable trace-level logging. See the [tracing documentation](https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/struct.EnvFilter.html#example-syntax)
  for more.
- `HTTP_TIMEOUT` (or `UV_HTTP_TIMEOUT`): If set, uv will use this value (in seconds) as the timeout
  for HTTP requests.
- `PYC_INVALIDATION_MODE`: The validation modes to use when run with `--compile`.
  See: [`PycInvalidationMode`](https://docs.python.org/3/library/py_compile.html#py_compile.PycInvalidationMode).
- `VIRTUAL_ENV`: Used to detect an activated virtual environment.
- `CONDA_PREFIX`: Used to detect an activated Conda environment.
- `PROMPT`: Used to detect the appropriate activation script after generating a virtual environment.
- `NU_VERSION`: Used to detect the appropriate activation script after generating a virtual environment.

## Custom CA Certificates

By default, uv loads certificates from the bundled `webpki-roots` crate. The `webpki-roots` are a
reliable set of trust roots from Mozilla, and including them in uv improves portability and
performance (especially on macOS, where reading the system trust store incurs a significant delay).

However, in some cases, you may want to use the platform's native certificate store, especially if
you're relying on a corporate trust root (e.g., for a mandatory proxy) that's included in your
system's certificate store. To instruct uv to use the system's trust store, run uv with the
`--native-tls` command-line flag, or set the `UV_NATIVE_TLS` environment variable to `true`.

If a direct path to the certificate is required (e.g., in CI), set the `SSL_CERT_FILE` environment
variable to the path of the certificate bundle, to instruct uv to use that file instead of the
system's trust store.

## Acknowledgements

uv's dependency resolver uses [PubGrub](https://github.com/pubgrub-rs/pubgrub) under the hood.
We're grateful to the PubGrub maintainers, especially [Jacob Finkelman](https://github.com/Eh2406),
for their support.

uv's Git implementation is based on [Cargo](https://github.com/rust-lang/cargo).

Some of uv's optimizations are inspired by the great work we've seen in
[pnpm](https://pnpm.io/), [Orogene](https://github.com/orogene/orogene), and
[Bun](https://github.com/oven-sh/bun). We've also learned a lot from Nathaniel
J. Smith's [Posy](https://github.com/njsmith/posy) and adapted its [trampoline](https://github.com/njsmith/posy/tree/main/src/trampolines/windows-trampolines/posy-trampoline)
for Windows support.

## License

uv is licensed under either of

- Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license ([LICENSE-MIT](LICENSE-MIT) or https://opensource.org/licenses/MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in uv by you, as defined in the Apache-2.0 license, shall be
dually licensed as above, without any additional terms or conditions.

<div align="center">
  <a target="_blank" href="https://astral.sh" style="background:none">
    <img src="https://raw.githubusercontent.com/astral-sh/uv/main/assets/svg/Astral.svg" alt="Made by Astral">
  </a>
</div>
