pip.conf index-url: use a private or mirror package index

index-url sets the package index pip installs from instead of PyPI. Put it in the [global] section of pip.conf (pip.ini on Windows), set the PIP_INDEX_URL environment variable, or pass --index-url on the command line. pip config list shows what pip actually reads.

[global]
index-url = https://pypi.example.com/simple

Set it and check it

cat > pip.conf <<'EOF'
[global]
index-url = https://pypi.example.com/simple
EOF
export PIP_CONFIG_FILE="$PWD/pip.conf"
pip config --disable-pip-version-check list
echo "--- with PIP_INDEX_URL set"
PIP_INDEX_URL=https://mirror.example.org/simple pip config --disable-pip-version-check list

:env:.config-file='/tmp/work/pip.conf'
global.index-url='https://pypi.example.com/simple'
--- with PIP_INDEX_URL set
:env:.config-file='/tmp/work/pip.conf'
:env:.index-url='https://mirror.example.org/simple'
global.index-url='https://pypi.example.com/simple'

PIP_CONFIG_FILE points pip at one specific file, which is handy in CI and containers. Values that come from environment variables are listed with the :env: prefix, and PIP_INDEX_URL wins over the file. pip config set global.index-url URL writes the user configuration file instead and prints its path.

Where pip looks

Files are read from global to site, and later ones override earlier ones. Environment variables (PIP_<OPTION>) override all files, and command-line options override everything. pip config debug prints every file pip considered and whether it exists.

index-url vs extra-index-url

[global]
index-url = https://pypi.example.com/simple
extra-index-url = https://pypi.org/simple

extra-index-url adds indexes; pip then picks the best matching version across all of them.

Credentials

Do not put passwords in pip.conf. Use a keyring backend, a .netrc file, or let CI inject the full URL through PIP_INDEX_URL as a secret.