The Jupyter contributor community is proud to announce JupyterLab 4.0, the next major release of our full-featured development environment. The package is now available on PyPI and conda-forge. You can upgrade by running pip install --upgrade jupyterlab or conda install -c conda-forge jupyterlab. We have updated our JupyterLab Documentation for this new version.
You can read our full announcement here:
Great release!
Over the last months I learned so much through jupyterlab.
Thanks for not breaking any of my kernels, therefore i can forgive breaking most of my extensions 
It seems conda update --all won’t upgrade to JupyterLab 4.0. Is this expected (like maybe I have to wait until it is fed into the “stable channels” or something?)
Joining this question. I don’t understand how to upgrade to JupyterLab 4.0.
I’m not sure which conda channel you’re using, but using conda-forge, you should be able to install version 4: conda install -c conda-forge jupyterlab=4
That works well! Thank you!
Guys please post a compatibility matrix somewhere prominent.
I have developed an extension with the cookiecutter template, JL 3.x, and now to migrate to JL 4.x leaving backward compatibility (even only partial) with the workflows I had in 3.x is a painful task, even using the recommended migration tool here.
Anyway I have tried 4.x and it seems full of improvements, thanks for your great work guys, but in my personal opinion it is still frustrating to be able to develop anything from this framework.
A great improvement, really appreciated, was the one related to the release cycle, now that a “pip install” of the extension is enough. I hope it will keep improving like this.
@gianfa there are plans to address these points by a new working group being bootstrapped, feel welcome to join with constructive feedback: Plugin and extension system working group · Issue #209 · jupyterlab/team-compass · GitHub
