Lost colorization in Jupyter Notebook

Anaconda3 is installed and updated with all the latest versions ov serval apps including JupyterLab and Jupyter.

JupyterLab operates without problems, but Jupyter has lost all colorization. No syntax colors for code or markup; all is in black and white. Sometimes, rarely, the colorization for Jupyter returns after app startup.

Is there an easy fix for this?

I’ve considered uninstalling Jupyter via conda and then reinstalling, but I have a long-running cell in JupyterLab that I don’t want affected.

Will uninstalling Jupyter via conda and then reinstalling affect a running JupyterLab?

It could be a problem with your browser. Have you tried clearing your browser cache and/or site settings? You could also test using an incognito window since that should ignore your existing browser cache.

Cleared cache; didn’t solve issue.

Jupyter would not launch to the incognito window!

Are there any errors in your browser devtools console?

Otherwise it might be worth creating a new conda env, installing Jupyter from scratch and running it on a different port. That way you can test without interrupting your long-running notebook.


Although clearing the browser cache had no effect “initially”, it appears you may be correct about the browser being the culprit. Suddenly, after about 30+ minutes of use, the notebook regained colorization.

It’s still can’t definitively identify what the cause is though. I’ll keep working on it.

If needed, I’ll follow you additional suggestion.

Thank you so much for you helpful insight!