Read more details about the changes currently taking place in the Jupyter Ecosystem in this team-compass issue.
Any extension developed for Notebook < 7 or NbClassic will not be compatible with Notebook 7 and upwards.
NbClassic and Notebook 7
You can install NbClassic, Notebook 7 and JupyterLab, all three of
which will be providing different user interfaces that will be available
on the same server. When Notebook 7 is available, the NbClassic UI, will
be served at the /nbclassic/tree base path rather than the
base path /tree used otherwise. If you are using Notebook 7 along
with NbClassic, you wil also have JupyterLab installed as it is a
dependency of Notebook 7, and these front ends will be available
through the following base paths: JupyterLab at /lab, Notebook 7 at
/tree, and NbClassic at /nbclassic/tree.
NbClassic and Notebook 6.5.x
As NbClassic provides the static assets for Notebook 6.5.x, while
having both installed should cause no issues, the user interface provided
by these two packages will be the same. These UIs would be available in
different servers. An NbClassic instance will be at a server with the
/tree path and opening a Notebook 6.5.x instance will open on a
different server with the /tree path as well, presenting the same
static assets. When starting an instance of JupyterLab you will be able
to access the classic view of Notebook with NbClassic served on the same
server at /tree.
NbClassic and Notebook <= 6.4.x
When using NbClassic and Notebook <= 6.4.x you can expect that these UIs
will not be only presented at different servers, meaning they will both
be available at their respective server under /tree but they
may also differ as potential changes to the NbClassic UI will not be
reflected in Notebook versions <= 6.4.x. In this case as well, you would
be able to access the classic view of Notebook with NbClassic served on
the same server, at /tree.
NbClassic and JupyterLab 3.x
When only JupyterLab 3.x is installed, then NbClassic does not have to be
explicitly installed as JupyterLab 3.x depends on it. They will run on
the same server, and are reachable via /tree for NbClassic and
/lab for JupyterLab.
NbClassic and JupyterLab 4.x
When only JupyterLab 4.x is installed, then NbClassic has to be installed
explictly. They will run on the same server, and are reachable via
/tree for NbClassic, and /lab for JupyterLab.
NbClassic Independently
When you choose to install only NbClassic via pip install nbclassic,
the classic Notebook UI will be presented at the /tree path. As the
other frontends are not installed, attempting to access the other paths
will return errors. Note that NbClassic being a Jupyter Server extension,
indicated Jupyter Server will be available. This provides an additional
way to view the NbClassic frontend. You would be able to manually
enable the extension when running an instance of Jupyter Server,
> jupyter server --ServerApp.jpserver_extensions="nbclassic=True",
which will provide the NbClassic frontend at /tree path when visited.