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Environment variables

uv defines and respects the following environment variables:

UV_BREAK_SYSTEM_PACKAGES

added in 0.1.32

Equivalent to the --break-system-packages command-line argument. If set to true, uv will allow the installation of packages that conflict with system-installed packages.

WARNING: UV_BREAK_SYSTEM_PACKAGES=true is intended for use in continuous integration (CI) or containerized environments and should be used with caution, as modifying the system Python can lead to unexpected behavior.

UV_BUILD_CONSTRAINT

added in 0.2.34

Equivalent to the --build-constraints command-line argument. If set, uv will use this file as constraints for any source distribution builds. Uses space-separated list of files.

UV_CACHE_DIR

added in 0.0.5

Equivalent to the --cache-dir command-line argument. If set, uv will use this directory for caching instead of the default cache directory.

UV_COMPILE_BYTECODE

added in 0.3.3

Equivalent to the --compile-bytecode command-line argument. If set, uv will compile Python source files to bytecode after installation.

UV_COMPILE_BYTECODE_TIMEOUT

added in 0.7.22

Timeout (in seconds) for bytecode compilation.

UV_CONCURRENT_BUILDS

added in 0.1.43

Sets the maximum number of source distributions that uv will build concurrently at any given time.

UV_CONCURRENT_DOWNLOADS

added in 0.1.43

Sets the maximum number of in-flight concurrent downloads that uv will perform at any given time.

UV_CONCURRENT_INSTALLS

added in 0.1.45

Controls the number of threads used when installing and unzipping packages.

UV_CONFIG_FILE

added in 0.1.34

Equivalent to the --config-file command-line argument. Expects a path to a local uv.toml file to use as the configuration file.

UV_CONSTRAINT

added in 0.1.36

Equivalent to the --constraints command-line argument. If set, uv will use this file as the constraints file. Uses space-separated list of files.

UV_CREDENTIALS_DIR

added in 0.8.15

The directory for storage of credentials when using a plain text backend.

UV_CUSTOM_COMPILE_COMMAND

added in 0.1.23

Equivalent to the --custom-compile-command command-line argument.

Used to override uv in the output header of the requirements.txt files generated by uv pip compile. Intended for use-cases in which uv pip compile is called from within a wrapper script, to include the name of the wrapper script in the output file.

UV_DEFAULT_INDEX

added in 0.4.23

Equivalent to the --default-index command-line argument. If set, uv will use this URL as the default index when searching for packages.

UV_DEV

added in 0.8.7

Equivalent to the --dev command-line argument. If set, uv will include development dependencies.

UV_DOWNLOAD_URL

added in 0.8.4

The URL from which to download uv using the standalone installer. By default, installs from uv's GitHub Releases. INSTALLER_DOWNLOAD_URL is also supported as an alias, for backwards compatibility.

UV_ENV_FILE

added in 0.4.30

.env files from which to load environment variables when executing uv run commands.

UV_EXCLUDE

added in 0.9.8

Equivalent to the --excludes command-line argument. If set, uv will use this as the excludes file. Uses space-separated list of files.

UV_EXCLUDE_NEWER

added in 0.2.12

Equivalent to the --exclude-newer command-line argument. If set, uv will exclude distributions published after the specified date.

UV_EXTRA_INDEX_URL

added in 0.1.3

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. (Deprecated: use UV_INDEX instead.)

UV_FIND_LINKS

added in 0.4.19

Equivalent to the --find-links command-line argument. If set, uv will use this comma-separated list of additional locations to search for packages.

UV_FORK_STRATEGY

added in 0.5.9

Equivalent to the --fork-strategy argument. Controls version selection during universal resolution.

UV_FROZEN

added in 0.4.25

Equivalent to the --frozen command-line argument. If set, uv will run without updating the uv.lock file.

UV_GITHUB_TOKEN

added in 0.4.10

Equivalent to the --token argument for self update. A GitHub token for authentication.

UV_GIT_LFS

added in 0.5.19

Enables fetching files stored in Git LFS when installing a package from a Git repository.

UV_HIDE_BUILD_OUTPUT

added in 0.9.14

Suppress output from the build backend when building source distributions, even in the event of build failures.

UV_HTTP_RETRIES

added in 0.7.21

The number of retries for HTTP requests. (default: 3)

UV_HTTP_TIMEOUT

added in 0.1.7

Timeout (in seconds) for HTTP requests. (default: 30 s)

UV_INDEX

added in 0.4.23

Equivalent to the --index command-line argument. If set, uv will use this space-separated list of URLs as additional indexes when searching for packages.

UV_INDEX_STRATEGY

added in 0.1.29

Equivalent to the --index-strategy command-line argument.

For example, if set to unsafe-best-match, uv will consider versions of a given package available across all index URLs, rather than limiting its search to the first index URL that contains the package.

UV_INDEX_URL

added in 0.0.5

Equivalent to the --index-url command-line argument. If set, uv will use this URL as the default index when searching for packages. (Deprecated: use UV_DEFAULT_INDEX instead.)

UV_INDEX_{name}_PASSWORD

added in 0.4.23

Provides the HTTP Basic authentication password for a named index.

The name parameter is the name of the index. For example, given an index named foo, the environment variable key would be UV_INDEX_FOO_PASSWORD.

UV_INDEX_{name}_USERNAME

added in 0.4.23

Provides the HTTP Basic authentication username for a named index.

The name parameter is the name of the index. For example, given an index named foo, the environment variable key would be UV_INDEX_FOO_USERNAME.

UV_INIT_BUILD_BACKEND

added in 0.8.2

Equivalent to the --build-backend argument for uv init. Determines the default backend to use when creating a new project.

UV_INSECURE_HOST

added in 0.3.5

Equivalent to the --allow-insecure-host argument.

UV_INSECURE_NO_ZIP_VALIDATION

added in 0.8.6

Disable ZIP validation for streamed wheels and ZIP-based source distributions.

WARNING: Disabling ZIP validation can expose your system to security risks by bypassing integrity checks and allowing uv to install potentially malicious ZIP files. If uv rejects a ZIP file due to failing validation, it is likely that the file is malformed; consider filing an issue with the package maintainer.

UV_INSTALLER_GHE_BASE_URL

added in 0.5.0

The URL from which to download uv using the standalone installer and self update feature, in lieu of the default GitHub Enterprise URL.

UV_INSTALLER_GITHUB_BASE_URL

added in 0.5.0

The URL from which to download uv using the standalone installer and self update feature, in lieu of the default GitHub URL.

UV_INSTALL_DIR

added in 0.5.0

The directory in which to install uv using the standalone installer and self update feature. Defaults to ~/.local/bin.

UV_ISOLATED

added in 0.8.14

Equivalent to the --isolated command-line argument. If set, uv will avoid discovering a pyproject.toml or uv.toml file.

UV_KEYRING_PROVIDER

added in 0.1.19

Equivalent to the --keyring-provider command-line argument. If set, uv will use this value as the keyring provider.

UV_LIBC

added in 0.7.22

Overrides the environment-determined libc on linux systems when filling in the current platform within Python version requests. Options are: gnu, gnueabi, gnueabihf, musl, and none.

UV_LINK_MODE

added in 0.1.40

Equivalent to the --link-mode command-line argument. If set, uv will use this as a link mode.

UV_LOCKED

added in 0.4.25

Equivalent to the --locked command-line argument. If set, uv will assert that the uv.lock remains unchanged.

UV_LOG_CONTEXT

added in 0.6.4

Add additional context and structure to log messages.

If logging is not enabled, e.g., with RUST_LOG or -v, this has no effect.

UV_MANAGED_PYTHON

added in 0.6.8

Require use of uv-managed Python versions.

UV_NATIVE_TLS

added in 0.1.19

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.

UV_NO_BINARY

added in 0.5.30

Equivalent to the --no-binary command-line argument. If set, uv will install all packages from source. The resolver will still use pre-built wheels to extract package metadata, if available.

UV_NO_BINARY_PACKAGE

added in 0.5.30

Equivalent to the --no-binary-package command line argument. If set, uv will not use pre-built wheels for the given space-delimited list of packages.

UV_NO_BUILD

added in 0.1.40

Equivalent to the --no-build command-line argument. If set, uv will not build source distributions.

UV_NO_BUILD_ISOLATION

added in 0.1.40

Equivalent to the --no-build-isolation command-line argument. If set, uv will skip isolation when building source distributions.

UV_NO_BUILD_PACKAGE

added in 0.6.5

Equivalent to the --no-build-package command line argument. If set, uv will not build source distributions for the given space-delimited list of packages.

UV_NO_CACHE

added in 0.1.2

Equivalent to the --no-cache command-line argument. If set, uv will not use the cache for any operations.

UV_NO_CONFIG

added in 0.2.30

Equivalent to the --no-config command-line argument. If set, uv will not read any configuration files from the current directory, parent directories, or user configuration directories.

UV_NO_DEFAULT_GROUPS

added in 0.9.9

Equivalent to the --no-default-groups command-line argument. If set, uv will not select the default dependency groups defined in tool.uv.default-groups.

UV_NO_DEV

added in 0.8.7

Equivalent to the --no-dev command-line argument. If set, uv will exclude development dependencies.

UV_NO_EDITABLE

added in 0.6.15

Equivalent to the --no-editable command-line argument. If set, uv installs or exports any editable dependencies, including the project and any workspace members, as non-editable.

UV_NO_ENV_FILE

added in 0.4.30

Ignore .env files when executing uv run commands.

UV_NO_GITHUB_FAST_PATH

added in 0.7.13

Disable GitHub-specific requests that allow uv to skip git fetch in some circumstances.

UV_NO_GROUP

added in 0.9.8

Equivalent to the --no-group command-line argument. If set, uv will disable the specified dependency groups for the given space-delimited list of packages.

UV_NO_HF_TOKEN

added in 0.8.1

Disable Hugging Face authentication, even if HF_TOKEN is set.

UV_NO_INSTALLER_METADATA

added in 0.5.7

Skip writing uv installer metadata files (e.g., INSTALLER, REQUESTED, and direct_url.json) to site-packages .dist-info directories.

UV_NO_MANAGED_PYTHON

added in 0.6.8

Disable use of uv-managed Python versions.

UV_NO_MODIFY_PATH

added in 0.8.4

Avoid modifying the PATH environment variable when installing uv using the standalone installer and self update feature. INSTALLER_NO_MODIFY_PATH is also supported as an alias, for backwards compatibility.

UV_NO_PROGRESS

added in 0.2.28

Equivalent to the --no-progress command-line argument. Disables all progress output. For example, spinners and progress bars.

UV_NO_SOURCES

added in 0.9.8

Equivalent to the --no-sources command-line argument. If set, uv will ignore [tool.uv.sources] annotations when resolving dependencies.

UV_NO_SYNC

added in 0.4.18

Equivalent to the --no-sync command-line argument. If set, uv will skip updating the environment.

UV_NO_VERIFY_HASHES

added in 0.5.3

Equivalent to the --no-verify-hashes argument. Disables hash verification for requirements.txt files.

UV_NO_WRAP

added in 0.0.5

Use to disable line wrapping for diagnostics.

UV_OFFLINE

added in 0.5.9

Equivalent to the --offline command-line argument. If set, uv will disable network access.

UV_OVERRIDE

added in 0.2.22

Equivalent to the --overrides command-line argument. If set, uv will use this file as the overrides file. Uses space-separated list of files.

UV_PRERELEASE

added in 0.1.16

Equivalent to the --prerelease command-line argument. For example, if set to allow, uv will allow pre-release versions for all dependencies.

UV_PREVIEW

added in 0.1.37

Equivalent to the --preview argument. Enables preview mode.

UV_PREVIEW_FEATURES

added in 0.8.4

Equivalent to the --preview-features argument. Enables specific preview features.

UV_PROJECT

added in 0.4.4

Equivalent to the --project command-line argument.

UV_PROJECT_ENVIRONMENT

added in 0.4.4

Specifies the path to the directory to use for a project virtual environment.

See the project documentation for more details.

UV_PUBLISH_CHECK_URL

added in 0.4.30

Don't upload a file if it already exists on the index. The value is the URL of the index.

UV_PUBLISH_INDEX

added in 0.5.8

Equivalent to the --index command-line argument in uv publish. If set, uv the index with this name in the configuration for publishing.

UV_PUBLISH_NO_ATTESTATIONS

added in 0.9.12

Equivalent to the --no-attestations command-line argument in uv publish. If set, uv will skip uploading any collected attestations for the published distributions.

UV_PUBLISH_PASSWORD

added in 0.4.16

Equivalent to the --password command-line argument in uv publish. If set, uv will use this password for publishing.

UV_PUBLISH_TOKEN

added in 0.4.16

Equivalent to the --token command-line argument in uv publish. If set, uv will use this token (with the username __token__) for publishing.

UV_PUBLISH_URL

added in 0.4.16

Equivalent to the --publish-url command-line argument. The URL of the upload endpoint of the index to use with uv publish.

UV_PUBLISH_USERNAME

added in 0.4.16

Equivalent to the --username command-line argument in uv publish. If set, uv will use this username for publishing.

UV_PYPY_INSTALL_MIRROR

added in 0.2.35

Managed PyPy installations are downloaded from python.org.

This variable can be set to a mirror URL to use a different source for PyPy installations. The provided URL will replace https://downloads.python.org/pypy in, e.g., https://downloads.python.org/pypy/pypy3.8-v7.3.7-osx64.tar.bz2. Distributions can be read from a local directory by using the file:// URL scheme.

UV_PYTHON

added in 0.1.40

Equivalent to the --python command-line argument. If set to a path, uv will use this Python interpreter for all operations.

UV_PYTHON_BIN_DIR

added in 0.4.29

Specifies the directory to place links to installed, managed Python executables.

UV_PYTHON_CACHE_DIR

added in 0.7.0

Specifies the directory for caching the archives of managed Python installations before installation.

UV_PYTHON_CPYTHON_BUILD

added in 0.8.14

Pin managed CPython versions to a specific build version.

For CPython, this should be the build date (e.g., "20250814").

UV_PYTHON_DOWNLOADS

added in 0.3.2

Equivalent to the python-downloads setting and, when disabled, the --no-python-downloads option. Whether uv should allow Python downloads.

UV_PYTHON_DOWNLOADS_JSON_URL

added in 0.6.13

Managed Python installations information is hardcoded in the uv binary.

This variable can be set to a local path or URL pointing to a JSON list of Python installations to override the hardcoded list.

This allows customizing the URLs for downloads or using slightly older or newer versions of Python than the ones hardcoded into this build of uv.

UV_PYTHON_GRAALPY_BUILD

added in 0.8.14

Pin managed GraalPy versions to a specific build version.

For GraalPy, this should be the GraalPy version (e.g., "24.2.2").

UV_PYTHON_INSTALL_BIN

added in 0.8.0

Whether to install the Python executable into the UV_PYTHON_BIN_DIR directory.

UV_PYTHON_INSTALL_DIR

added in 0.2.22

Specifies the directory for storing managed Python installations.

UV_PYTHON_INSTALL_MIRROR

added in 0.2.35

Managed Python installations are downloaded from the Astral python-build-standalone project.

This variable can be set to a mirror URL to use a different source for Python installations. The provided URL will replace https://github.com/astral-sh/python-build-standalone/releases/download in, e.g., https://github.com/astral-sh/python-build-standalone/releases/download/20240713/cpython-3.12.4%2B20240713-aarch64-apple-darwin-install_only.tar.gz. Distributions can be read from a local directory by using the file:// URL scheme.

UV_PYTHON_INSTALL_REGISTRY

added in 0.8.0

Whether to install the Python executable into the Windows registry.

UV_PYTHON_PREFERENCE

added in 0.3.2

Whether uv should prefer system or managed Python versions.

UV_PYTHON_PYODIDE_BUILD

added in 0.8.14

Pin managed Pyodide versions to a specific build version.

For Pyodide, this should be the Pyodide version (e.g., "0.28.1").

UV_PYTHON_PYPY_BUILD

added in 0.8.14

Pin managed PyPy versions to a specific build version.

For PyPy, this should be the PyPy version (e.g., "7.3.20").

UV_REQUEST_TIMEOUT

added in 0.1.6

Timeout (in seconds) for HTTP requests. Equivalent to UV_HTTP_TIMEOUT.

UV_REQUIRE_HASHES

added in 0.1.34

Equivalent to the --require-hashes command-line argument. If set to true, uv will require that all dependencies have a hash specified in the requirements file.

UV_RESOLUTION

added in 0.1.27

Equivalent to the --resolution command-line argument. For example, if set to lowest-direct, uv will install the lowest compatible versions of all direct dependencies.

UV_S3_ENDPOINT_URL

added in 0.8.21

The URL to treat as an S3-compatible storage endpoint. Requests to this endpoint will be signed using AWS Signature Version 4 based on the AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_PROFILE, and AWS_CONFIG_FILE environment variables.

UV_SKIP_WHEEL_FILENAME_CHECK

added in 0.8.23

Avoid verifying that wheel filenames match their contents when installing wheels. This is not recommended, as wheels with inconsistent filenames should be considered invalid and corrected by the relevant package maintainers; however, this option can be used to work around invalid artifacts in rare cases.

UV_STACK_SIZE

added in 0.0.5

Use to set the stack size used by uv.

The value is in bytes, and if both UV_STACK_SIZE are RUST_MIN_STACK unset, uv uses a 4MB (4194304) stack. UV_STACK_SIZE takes precedence over RUST_MIN_STACK.

Unlike the normal RUST_MIN_STACK semantics, this can affect main thread stack size, because we actually spawn our own main2 thread to work around the fact that Windows' real main thread is only 1MB. That thread has size max(UV_STACK_SIZE, 1MB).

UV_SYSTEM_PYTHON

added in 0.1.18

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) or containerized environments and should be used with caution, as modifying the system Python can lead to unexpected behavior.

UV_TEST_NO_HTTP_RETRY_DELAY

added in 0.7.21

Used to disable delay for HTTP retries in tests.

UV_TOOL_BIN_DIR

added in 0.3.0

Specifies the "bin" directory for installing tool executables.

UV_TOOL_DIR

added in 0.2.16

Specifies the directory where uv stores managed tools.

UV_TORCH_BACKEND

added in 0.6.9

Equivalent to the --torch-backend command-line argument (e.g., cpu, cu126, or auto).

UV_UNMANAGED_INSTALL

added in 0.5.0

Used ephemeral environments like CI to install uv to a specific path while preventing the installer from modifying shell profiles or environment variables.

UV_UPLOAD_HTTP_TIMEOUT

added in 0.9.1

Timeout (in seconds) for only upload HTTP requests. (default: 900 s)

UV_VENV_CLEAR

added in 0.8.0

Equivalent to the --clear command-line argument. If set, uv will remove any existing files or directories at the target path.

UV_VENV_SEED

added in 0.5.21

Install seed packages (one or more of: pip, setuptools, and wheel) into the virtual environment created by uv venv.

Note that setuptools and wheel are not included in Python 3.12+ environments.

UV_WORKING_DIRECTORY

added in 0.9.1

Equivalent to the --directory command-line argument.

Externally defined variables

uv also reads the following externally defined environment variables:

ALL_PROXY

added in 0.1.38

General proxy for all network requests.

ANDROID_API_LEVEL

added in 0.8.16

Used with --python-platform aarch64-linux-android and related variants to set the Android API level. (i.e., the minimum supported Android API level).

Defaults to 24.

APPDATA

added in 0.1.42

Path to user-level configuration directory on Windows systems.

AWS_ACCESS_KEY_ID

added in 0.8.21

The AWS access key ID to use when signing S3 requests.

AWS_CONFIG_FILE

added in 0.8.21

The AWS config file to use when signing S3 requests.

AWS_DEFAULT_REGION

added in 0.8.21

The default AWS region to use when signing S3 requests, if AWS_REGION is not set.

AWS_PROFILE

added in 0.8.21

The AWS profile to use when signing S3 requests.

AWS_REGION

added in 0.8.21

The AWS region to use when signing S3 requests.

AWS_SECRET_ACCESS_KEY

added in 0.8.21

The AWS secret access key to use when signing S3 requests.

AWS_SESSION_TOKEN

added in 0.8.21

The AWS session token to use when signing S3 requests.

AWS_SHARED_CREDENTIALS_FILE

added in 0.8.21

The AWS shared credentials file to use when signing S3 requests.

BASH_VERSION

added in 0.1.28

Used to detect Bash shell usage.

CLICOLOR_FORCE

added in 0.1.32

Use to control color via anstyle.

COLUMNS

added in 0.6.2

Overrides terminal width used for wrapping. This variable is not read by uv directly.

This is a quasi-standard variable, described, e.g., in ncurses(3x).

CONDA_DEFAULT_ENV

added in 0.5.0

Used to determine the name of the active Conda environment.

CONDA_PREFIX

added in 0.0.5

Used to detect the path of an active Conda environment.

DEPENDABOT

added in 0.9.11

Used to determine if we're running in Dependabot.

FISH_VERSION

added in 0.1.28

Used to detect Fish shell usage.

FORCE_COLOR

added in 0.2.7

Forces colored output regardless of terminal support.

See force-color.org.

GITHUB_ACTIONS

added in 0.4.16

Indicates that the current process is running in GitHub Actions.

uv publish may attempt trusted publishing flows when set to true.

GITLAB_CI

added in 0.8.18

Indicates that the current process is running in GitLab CI.

uv publish may attempt trusted publishing flows when set to true.

HF_TOKEN

added in 0.8.1

Authentication token for Hugging Face requests. When set, uv will use this token when making requests to https://huggingface.co/ and any subdomains.

HOME

added in 0.0.5

The standard HOME env var.

HTTPS_PROXY

added in 0.1.38

Proxy for HTTPS requests.

HTTP_PROXY

added in 0.1.38

Proxy for HTTP requests.

HTTP_TIMEOUT

added in 0.1.7

Timeout (in seconds) for HTTP requests. Equivalent to UV_HTTP_TIMEOUT.

IPHONEOS_DEPLOYMENT_TARGET

added in 0.8.16

Used with --python-platform arm64-apple-ios and related variants to set the deployment target (i.e., the minimum supported iOS version).

Defaults to 13.0.

JPY_SESSION_NAME

added in 0.2.6

Used to detect when running inside a Jupyter notebook.

KSH_VERSION

added in 0.2.33

Used to detect Ksh shell usage.

LOCALAPPDATA

added in 0.3.3

Used to look for Microsoft Store Pythons installations.

MACOSX_DEPLOYMENT_TARGET

added in 0.1.42

Used with --python-platform macos and related variants to set the deployment target (i.e., the minimum supported macOS version).

Defaults to 13.0, the least-recent non-EOL macOS version at time of writing.

NETRC

added in 0.1.16

Use to set the .netrc file location.

NO_COLOR

added in 0.2.7

Disables colored output (takes precedence over FORCE_COLOR).

See no-color.org.

NO_PROXY

added in 0.1.38

Comma-separated list of hostnames (e.g., example.com) and/or patterns (e.g., 192.168.1.0/24) that should bypass the proxy.

NU_VERSION

added in 0.1.16

Used to detect NuShell usage.

PAGER

added in 0.4.18

The standard PAGER posix env var. Used by uv to configure the appropriate pager.

PATH

added in 0.0.5

The standard PATH env var.

PROMPT

added in 0.1.16

Used to detect the use of the Windows Command Prompt (as opposed to PowerShell).

PWD

added in 0.0.5

The standard PWD posix env var.

PYC_INVALIDATION_MODE

added in 0.1.7

The validation modes to use when run with --compile.

See PycInvalidationMode.

PYTHONPATH

added in 0.1.22

Adds directories to Python module search path (e.g., PYTHONPATH=/path/to/modules).

PYX_API_KEY

added in 0.8.15

The pyx API key (e.g., sk-pyx-...).

PYX_API_URL

added in 0.8.15

The URL of the pyx Simple API server.

PYX_AUTH_TOKEN

added in 0.8.15

The pyx authentication token (e.g., eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...), as output by uv auth token.

PYX_CDN_DOMAIN

added in 0.8.15

The domain of the pyx CDN.

PYX_CREDENTIALS_DIR

added in 0.8.15

Specifies the directory where uv stores pyx credentials.

RUST_BACKTRACE

added in 0.7.22

If set, it can be used to display more stack trace details when a panic occurs. This is used by uv particularly on windows to show more details during a platform exception.

For example:

  • RUST_BACKTRACE=1 will print a short backtrace.
  • RUST_BACKTRACE=full will print a full backtrace.

See the Rust backtrace documentation for more.

RUST_LOG

added in 0.0.5

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=uv=debug is the equivalent of adding --verbose to the command line
  • RUST_LOG=trace will enable trace-level logging.

See the tracing documentation for more.

RUST_MIN_STACK

added in 0.5.19

Use to set the stack size used by uv.

The value is in bytes, and if both UV_STACK_SIZE are RUST_MIN_STACK unset, uv uses a 4MB (4194304) stack. UV_STACK_SIZE takes precedence over RUST_MIN_STACK.

Prefer setting UV_STACK_SIZE, since RUST_MIN_STACK also affects subprocesses, such as build backends that use Rust code.

Unlike the normal RUST_MIN_STACK semantics, this can affect main thread stack size, because we actually spawn our own main2 thread to work around the fact that Windows' real main thread is only 1MB. That thread has size max(RUST_MIN_STACK, 1MB).

SHELL

added in 0.1.16

The standard SHELL posix env var.

SSL_CERT_DIR

added in 0.9.10

Custom path for certificate bundles for SSL connections. Multiple entries are supported separated using a platform-specific delimiter (: on Unix, ; on Windows).

Takes precedence over UV_NATIVE_TLS when set.

SSL_CERT_FILE

added in 0.1.14

Custom certificate bundle file path for SSL connections.

Takes precedence over UV_NATIVE_TLS when set.

SSL_CLIENT_CERT

added in 0.2.11

If set, uv will use this file for mTLS authentication. This should be a single file containing both the certificate and the private key in PEM format.

SYSTEMDRIVE

added in 0.4.26

Path to system-level configuration directory on Windows systems.

TRACING_DURATIONS_FILE

added in 0.0.5

Use to create the tracing durations file via the tracing-durations-export feature.

USERPROFILE

added in 0.0.5

Path to root directory of user's profile on Windows systems.

UV

added in 0.6.0

The path to the binary that was used to invoke uv.

This is propagated to all subprocesses spawned by uv.

If the executable was invoked through a symbolic link, some platforms will return the path of the symbolic link and other platforms will return the path of the symbolic link’s target.

See https://doc.rust-lang.org/std/env/fn.current_exe.html#security for security considerations.

VIRTUAL_ENV

added in 0.0.5

Used to detect an activated virtual environment.

VIRTUAL_ENV_DISABLE_PROMPT

added in 0.0.5

If set to 1 before a virtual environment is activated, then the virtual environment name will not be prepended to the terminal prompt.

XDG_BIN_HOME

added in 0.2.16

Path to directory where executables are installed.

XDG_CACHE_HOME

added in 0.1.17

Path to cache directory on Unix systems.

XDG_CONFIG_DIRS

added in 0.4.26

Path to system-level configuration directory on Unix systems.

XDG_CONFIG_HOME

added in 0.1.34

Path to user-level configuration directory on Unix systems.

XDG_DATA_HOME

added in 0.2.16

Path to directory for storing managed Python installations and tools.

ZDOTDIR

added in 0.2.25

Used to determine which .zshenv to use when Zsh is being used.

ZSH_VERSION

added in 0.1.28

Used to detect Zsh shell usage.

_CONDA_ROOT

added in 0.8.18

Used to determine the root install path of Conda.