JupyterLab is the next-gen UI for Project Jupyter. Approaching version 3.0, it is becoming more mature and provides an advanced computational environment, that can sometimes be compared to what traditional IDEs offer.
The single document mode as currently implemented in JupyterLab helps address this issue, but still displays a couple of visual cues that can be distracting to some users.
The goal of the `jupyterlab-classic` project is to look as close to the classic notebook UI as possible, while leveraging the efforts put in the development of JupyterLab itself and its extension system.
Technically speaking, `jupyterlab-classic` reuses **many** of the existing plugins for JupyterLab (notebook, toolbar), and also supports pre-built (federated) third-party extensions using the new distribution system added in 3.0. That way, extensions built for JupyterLab should also be compatible with `jupyterlab-classic`, as long as they can be added to the application shell provided by JupyterLab Classic.