/simple in PyPI index URL

In a PyPI (or PyPI-compatible) index URL, /simple refers to the “Simple API” defined by PEP 503.

What the “simple” index is

The Simple Repository API is a minimal, machine-friendly HTML interface that Python packaging tools (like pip, uv, poetry) use to discover and download packages.

Example:

https://pypi.org/simple/

or in Artifactory:

https://<host>/artifactory/api/pypi/<repo>/simple/

Why it’s called “simple”

It’s intentionally:

• Static
• HTML only (no JSON, no UI)
• Easy to parse by tools

Each page is just a list of links.

Example package page:

https://pypi.org/simple/requests/

HTML (simplified):

<a href="requests-2.31.0-py3-none-any.whl">requests-2.31.0</a>
<a href="requests-2.30.0.tar.gz">requests-2.30.0</a>

What /simple is used for

pip and similar tools require the Simple API for package resolution:

pip install requests \
  --index-url https://pypi.org/simple

or in requirements.txt:

--index-url https://artifactory.example.com/artifactory/api/pypi/my-repo/simple

What /simple is NOT

• ❌ Not a web UI
• ❌ Not browseable like /ui/native/...
• ❌ Not a REST JSON API

That’s why:

• You can open /ui/native/... in a browser
• You cannot meaningfully “browse” /simple except as raw HTML

Why your Artifactory URLs behave differently

In Artifactory:

If pip can’t access the /simple endpoint, it’s usually due to:

• Missing authentication
• Wrong repository type
• Proxy vs local repo mismatch
• Incorrect credentials in Docker build

Key takeaway

/simple is the standardized, minimal package index that pip uses to find packages. If an index URL doesn’t end in /simple, pip will not treat it as a valid PyPI repository.