CodeMirror, the text editor used for cells and file editors, has been updated to CodeMirror 6. This brings important accessibility and performance improvements as well as better customization capabilities. We have also improved the editor settings. Previously, users had to customize settings separately for each type of cell, the file editor, and the console editor. Now, you can change your settings in one place. It is now easier to use the default settings for all editors and to change some settings for specific cases. For example, you can now hide line numbers only for markdown cells.

Developers can now provide editor extensions, like themes and programming language parsers, through new application registries.

New extension manager

Starting with JupyterLab 3, extensions can be installed via Python packages (or other providers of prebuilt extensions).

In JupyterLab 4, building on this feature, the Extension Manager now includes extensions from pypi.org. This removes the build step from installation of extension when using Extension Manager.

Developers can provide an alternative package repository to display their own set of extensions.

Improved document search

The Search and Replace functionality has been improved with new features when searching in a notebook:

Highlight matches in rendered markdown cells
Search in selection
Multi-line search
Replace using regex capture-group references
Replace while preserving case

UI improvements

Some new elements have been added or changed in the UI:

Rework the running kernels section
"Add a new cell" button at the bottom of a notebook
Dialog to display keyboard shortcuts as in the Classic Notebook (use <kbd>Ctrl</kbd> + <kbd>Shift</kbd> + <kbd>H</kbd>)
Display the first line of cell input and outputs when they are collapsed

Accessibility improvements

JupyterLab is not yet fully accessible. Currently, we are focused on making Notebook 7 accessible. A big part of the code is shared, though, and the following accessibility improvements are in JupyterLab 4:

Improved focus and keyboard navigation in the file browser
More ARIA roles and labels were added to UI elements
Main menu collapses to a hamburger menu if there is not enough space to display all items.

Performance enhancements

JupyterLab is now faster, thanks to the following improvements:

CSS rules optimization: CSS selectors have been optimized to improve web browser performance when many elements are present on a page.
Upgrade to CodeMirror 6: Especially for notebooks with many cells, the new CodeMirror version is far more efficient than the previous version. Large notebooks should load more quickly.
Upgrade to MathJax 3: The mathematical equations renderer library has been been upgraded from v2 to v3 allowing faster rendering.
Notebook windowing: By rendering only the parts of a notebook that fit in the web browser viewport, JupyterLab is much more efficient. See an important note below.

Notebook windowing might add side effects for example if some cell outputs are displaying iframes. Therefore it is not yet the default value. But we recommend user to switch to it and report bugs to help us polish it. To test it, you need to set the user setting Notebook > Windowing mode to full. If you have issues with notebook rendering, try changing back to defer or none. (none should be used as a last resort, because it disables all optimizations.)

Real Time Collaboration

JupyterLab 3.6 already made significant improvements to the Real Time Collaboration (RTC) feature. The feature is now in a separate repository: jupyter_collaboration. The rationale is to limit the dependencies for users who don't need RTC. Separating RTC also helps organizations using JupyterLab that do not meet the specific requirements regarding file content management.

To enable RTC, install the jupyter-collaboration package with either pip or conda.

with pip: pip install "jupyter-collaboration>=1.0.0a0"
with conda: not yet available

RTC highlights in the standalone jupyter-collboration package, version 1.0.0, include:

Support for displaying multiple cursors and selections
Support for registration of new shared model types

For developers

Here are the main tool updates that will benefit extension authors and developers:

TypeScript v5
Yarn v3
React v18
Lumino v2

We recommend using Node.js v18 or newer, because older versions will reach end of life in 2023 or earlier (see Node release schedule).

To ease code migration to JupyterLab 4, developers should review the migration guide. A few existing extensions have already been migrated and can be used as examples:

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Package last updated on 15 May 2023

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