Is there a way to run custom javascript in a notebook? I tried using ~/.jupyter/custom/custom.js but it doesn’t seem to work.

Try passing --c.LabApp.custom_css=True to jupyterlab command. Relevant thread

Right. I’m deploying JupyterHub and I want to run custom javascript in the singleuser server. My goal is to customize the Kernel died unexpectedly message that pops up when the culling takes place.

This message pops up when frontend loses the websocket connection over the kernel running on the server. This can happen for many reasons not just for culling. For examples, in k8s environment, an OOM-killer can kill kernel on the server when it goes over the memory limit and that event shows up on …

I actually don’t really care about capturing the culling event. If I could change the message to: Kernel died unexpectedly. The server could have been killed as a result of your inactivity. then that would serve my purpose.

Is custom.js not supported anymore?

JupyterHub

manics May 29, 2025, 1:43pm 5

JupyterHub starts your singleuser server, typically Jupyter-Server with JupyterLab, so configuration of the front-end is mostly independent of JupyterHub.

In general it’d be helpful if you provide more information in your posts, have a read through

Topic		Replies	Views
~/.jupyter/custom/custom.js in jupyterhub/jupyterlab JupyterHub jupyterlab , help-wanted	6	1662	May 16, 2024
Custom CSS for jupyterhub-singleuser JupyterHub	7	714	September 11, 2024
How to add my own custom handlers in jupyter_server of jupyterhub platform JupyterHub help-wanted	2	1193	January 4, 2022
Custom.js file not executed JupyterLab	1	392	May 16, 2024
Cannot get notebook to load custom.js Notebook how-to , help-wanted	1	844	August 23, 2023

Is custom.js not supported anymore?

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