Notebook Tools

WLJS Notebook is fully accessible from the keyboard. One of the most important key combinations to know is Ctrl-P or ⌘-P, which brings up the Command Palette. From here, you have access to many small helper utilities, toolboxes, shortcuts:

Most of the utilities are notebooks themselves, which are evaluated in an isolated context whenever you click on a command palette item. You can find the information on each by clicking on icon, that will open the source notebook.

Shortcuts

Type any of those words to call the action:

Utilities

Every tool is a normal notebook, which is evaluated in the background and manipulates your working notebook, creating temporal cells whenever you call it from the palette.

Insert matrix

Creates a small widget in the cell below the focused one that helps to generate and insert matrices (lists of lists).

Place a cursor to the desired place in the cell and click Insert on the widget.

Special characters

Adds a toolbar to the notebook with special characters and snippets for writing nice-looking integrals, sums, and other constructs.

Select the piece of code and apply operation from the toolbar. Or place a cursor to a cell and insert a symbol/expression from the toolbar.

Format text

Adds a toolbar to the notebook for formatting code (font size, color, background, font face).

Select the piece of code and apply operation from the toolbar.

Upload ASCII data file

Creates a widget with importing wizard allowing to import CSV/TSV/DAT files, strip headers and insert a file to a cell as an iconized expression

Upload file

Basic widget for uploading files

Escape string

A helper tool to safely insert strings containing double quotes or other "unsafe" sequences. It will prompt a user to enter text and print a cell with the result.

Beautify code

Formats selected code or entire Wolfram input cell and attempts to apply syntax sugar if possible. If it fails, try Format code instead.

Select the code or place a cursor in the desired cell and call this tool from the command palette.

Format code

Formats selected code or entire Wolfram input cell. Action is the same as the previous one, but syntactic sugar is not applied.

Find in cells

Creates a floating search window and tries to find given expression in all visible cells of the notebook.

Show options

Attempts to discover the possible options of the given symbol in the cell and present them as an interactive table.

Start typing:

Plot[x, {x,0} 

and then call this widget. It will automatically find the unclosed bracket and fetch the head Plot. Click on the desired options in the table to insert them later, once you click on the green mark icon.

Notebook directory

Opens a notebook directory using OS's explorer.

Inline navigation helper (Slider)

A helper tool that creates a syntactic sugar inline widget on a selected number. It is used in 2D and 3D graphics or any other expression that supports Offload aka live-updates:

For example: select a number you want to manipulate and call this tool. It will create an inline widget with a slider. Evaluate your cell, manipulate the slider, and once you are satisfied, click on the mark icon.

Inline navigation helper (Drag)

A helper tool that creates a syntactic sugar inline widget on a selected pair {x,y} or triplet of numbers {x,y,z}. It is used in 2D and 3D graphics that support Offload aka live-updates:

For example: select a parameter's initial value you want to manipulate and call this tool. It will create an inline widget with a display and place a dragging gizmo on your 2D or 3D canvas. Evaluate your cell, drag the red dot (or 3D sphere), and once you are satisfied, click on the mark icon.

Text["Hello World", Offload[{-0.3,-0.3} + (*BB[*)({0,0})(*,*)(*"1:eJxTTMoPSmNkYGAoZgESHvk5KRAeB5AILqnMSXXKr0hjgskHleakFnMBGU6JydnpRfmleSlpzDDlQe5Ozvk5+UVFDGDwwR6dwcAAAAHdFiw="*)(*]BB*)]]

Inline navigation helper (Joystick)

A helper tool that creates a syntactic sugar inline widget on a selected pair {x,y}. It is used in 2D and any other expression that supports Offload aka live-updates and accepts a pair of numbers:

For example: select a parameter's initial value you want to manipulate and call this tool. It will create an inline widget with a joystick. Evaluate your cell, manipulate the joystick, and once you are satisfied, click on the mark icon.

Take a picture

Creates a widget, which uses any available video recording device to take a picture and place it as Image to a notebook's cell.

Record voice

Creates a widget which uses any available audio recording device to record live audio and place it to a cell as Audio object.

Crop image

Select an image or image-producing expression in your cell and call this tool. It will evaluate the selected expression and append an interactive widget allowing to do rectangular cropping.

Copy InputForm

Select the code in the cell and call this tool. It will strip all syntactic sugar from it and copy the pure InputForm of the expression to your clipboard.

Debugger

Debugger can be called from the top Misc menu or from the command palette. It is a tool that attaches to a notebook and a working kernel to intercept the evaluation process and monitor symbol changes.

What it can do:

What it cannot do:

Let's have a look at the interface:

Inspect is a central mode for debugging.

Inspecting Mode

It stops the current execution and allows you to interact with any other cells in the sub-session, enabling you to check the status of various symbols. You can write and evaluate other cells in Inspect mode.

For example, evaluate this one:

Do[k = i; Pause[1], {i, 100}];

Then switch to Inspect mode; it will pause the evaluation. Now, you can check the state of the k symbol by running a new cell with:

k

Watching Symbols

You can add a symbol to a tracking list to monitor its OwnValue in real-time automatically. It won't interrupt your execution unless you enable the checkbox for that option.

Breakpoints

In Wolfram Language, traditional breakpoints are difficult to implement since there is no source code file in the classical sense. Everything is an expression, and a breakpoint must be an expression as well.

There are two sources for breaking events, both of which immediately switch the kernel to Inspecting Mode.

Asserts

First, enable breaking on assertions from the dropdown menu in the top bar of the debugger. Then, whenever execution encounters False in an Assert, it will break.

For example:

Do[k = i; If[i > 6, Assert[False, "Hey"]]; Pause[1], {i, 100}];

This code will break automatically after 6 seconds. In Inspect mode, evaluating k will return 7.

If you track the k symbol at the same time, you will see it changing in the debugger window.

Symbols

When a symbol is assigned a new value, it generates an event in the debugger. Use the Break on checkbox to enable breaking.

For example:

Do[k = i; If[i > 6, test = Now]; Pause[1], {i, 100}];

This code will break after 6 iterations.

MCP Server

Model-Contex-Protocol server is always running in the background allowing LLM agents to interact with the notebook, run, edit, create cells and run code directly on the kernel. By the default it is available at:

This is a streaming (HTTP) MCP server with no authentification and / endpoint:

http://127.0.0.1:20564/

It also provides specific skills for various cell types, documentation and fits into 500-600 tokens at the start.

Installation

You can add it to your favourite coding tool as follows:

Claude Code

claude mcp add --transport http --scope user wljs-notebook http://127.0.0.1:20564/

Codex

codex mcp add wljs-notebook --url http://127.0.0.1:20564/

or add to it your config.toml as

[mcp_servers.wljs_notebook]
url = "http://127.0.0.1:20564/"

Tips

• Models are not allowed to create notebooks, but can find the "focused one"

• Mention focused cell in the prompt to avoid model to spend tokens for searching the whole notebook.

• Mention consult docs in the prompt for weaker models to force them checking the documentation on different cell types or features of interactive evaluation in Wolfram language cells.

• Use smaller models for grammar corrections, primitive tasks, i.e. Haiku 3.0 for example

• Anthropic models are generally better trained on Wolfram Language and their training data includes WLJS ecosyste

• It is cheaper to firstly find ficused notebook, then focused cell instead of using notebook context path, that will list all cells and their content (only first line)

Documentation for LLM

If needed MCP searches the documentiation on a given symbol using LLM-friendly compilation of our entire website: https://wljs.io/llms-full.txt

CLI

WLJS Notebook includes a small command-line interface for opening notebooks, inspecting the active notebook, editing cells, evaluating cells, and consulting local WLJS/Wolfram documentation.

Most commands print JSON to stdout. Errors are printed to stderr and return a non-zero exit code.

Basic usage

wljs .

Open the current directory in WLJS Notebook.

wljs path/to/file

or

wljs 'path/to/file'

Open a file by path

wljs help
wljs help --json
wljs describe
wljs version
wljs -v
wljs --version
wljs config
wljs status

Aliases for wljs describe:

wljs llm-help
wljs commands

Notebook inspection

wljs new

Create empty notebook.

wljs notebooks

List notebooks known to the application.

wljs focused

Print the id/hash of the currently focused notebook.

wljs context
wljs context --Notebook <notebook>

Print notebook context, including notebook id, cell list, and focused cell/selection when available. If --Notebook is omitted, the focused notebook is used.

wljs cells <notebook>

List cells in a notebook.

wljs focused-cell <notebook>

Print the currently focused cell and selected line range.

wljs lines <cell> <from> <to>

Read an inclusive, 1-indexed line range from a cell.

Example:

wljs lines cell123 1 40

Documentation

wljs docs <query>

Consult bundled WLJS skill docs first, then local Wolfram Language docs.

Useful queries include:

wljs docs javascript
wljs docs html
wljs docs markdown
wljs docs mermaid
wljs docs slides
wljs docs dynamics
wljs docs Manipulate
wljs docs EventHandler
wljs docs Offload
wljs docs Plot

Editing cells

wljs add <notebook> --content <text|@file|-> [--after <cell>] [--before <cell>] [--eval]

Add a new input cell.

Examples:

wljs add notebook123 --content-escaped '.md\none-line markdown'
wljs add notebook123 --content @example.wl
printf '.md\nHello World\n' | wljs add notebook123 --content - --eval

Use --content-escaped for converting \n to new lines.

Use --after or --before to choose where the new cell is inserted. These options are mutually exclusive.

Use --eval to evaluate the new cell after adding it.

wljs set-lines <cell> <from> <to> --content <text|@file|->

Replace an inclusive, 1-indexed line range in an input cell.

Example:

wljs set-lines cell123 3 5 --content 'replacement text'

wljs insert-lines <cell> <after> --content <text|@file|->

Insert content after a line. Use 0 to insert at the beginning.

Example:

wljs insert-lines cell123 0 --content '.md'

wljs delete-cell <cell>

Delete an input cell. Deleting an input cell also deletes its outputs.

Evaluation

wljs eval <cell>

Evaluate an input cell. Evaluation creates output cells.

wljs project <cell>

Project an input cell into a standalone window.

wljs wl '<wolfram-expression>'

Evaluate Wolfram Language directly in a ready kernel, without creating a notebook cell.

Examples:

wljs wl 'Total[Range[100]]'
wljs wl 'Plot[Sin[x], {x, 0, 10}]'

Content input

The --content option supports three forms.

Inline literal text

wljs add notebook123 --content 'one line'

Inline content is passed literally. A string like \n is not converted into a newline.

File input

wljs add notebook123 --content @example.wl

Reads content from example.wl.

Standard input

printf '.md\nHello World\n' | wljs add notebook123 --content -

or:

wljs add notebook123 --content - <<'EOF'
.md
Hello World
EOF

This is the recommended form for multiline content.

Cell type markers

Cell type is determined by the first line of the input cell.

Example Markdown cell:

wljs add notebook123 --content - --eval <<'EOF'
.md
# Hello World

This is a Markdown cell.
EOF

Printing option

Locate Print from the File menu or from the command palette to print an entire notebook as PDF.

Page breaks

Use Markdown cell with PageBreakAbove or PageBreakBelow symbols to force page breaks, i.e.:

.md

<PageBreakAbove/>

Application styles

You can apply custom CSS styles to all notebooks by adding them via Settings → Custom CSS. These styles are injected into the document head and apply globally.

Adding global styles

The styles will be applied to all windows automatically.

Available CSS classes

WLJS Notebook exposes predefined CSS classes for styling various elements:

Document structure

Cell states and types

Input cell languages

Markdown output

Styling examples

Change notebook background

.ccontainer {
  background: lightblue;
}

body {
  background: lightblue !important;
}

main {
  background: lightblue !important;
}

Style the input cell border marker

The vertical line on the left side of input cells:

.cin > :nth-child(2)::after {
  border-color: #5e8a8b;
}

Custom heading colors

.markdown h1 {
  color: #2e7d32;
}

.markdown h2 {
  color: #1565c0;
}

Fonts and colors

The following CSS variables control syntax highlighting, UI colors:

:root {
  /* Syntax highlighting */
  --editor-key-meta: #404740;
  --editor-key-keyword: #708;
  --editor-key-atom: #219;
  --editor-key-literal: #164;
  --editor-key-string: #a11;
  --editor-key-escape: #e40;
  --editor-key-variable: #00f;
  --editor-local-variable: #30a;
  --editor-key-type: #085;
  --editor-key-class: #167;
  --editor-special-variable: #256;
  --editor-key-property: #00c;
  --editor-key-comment: #940;
  --editor-key-invalid: #f00;
  --editor-outline: #696969;
}

UI fonts can be changed using the following patch:

:root {
  /* Typography UI */
  font-size: medium;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, 
    'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 
    'Open Sans', 'Helvetica Neue', sans-serif;
}

/* Typography code editor */
.cm-line {
  font-family: 'consolas' !important;
}

/* Typography textual cells */
.markdown {
  font-family: 'cursive' !important;
}

Installing Packages

How to install new packages locally?

Via Command Palette

Open your notebook and paste the GitHub link to a repo⁺ or URL to .paclet file to the command palette located on the top bar.

Via LPM

Create a new cell and insert:

LPMRepositories[{
    "Github" -> "https://github.com/user/MyLibrary"
}]

<<MyLibrary`

or using direct link to a paclet file

LPMRepositories[{
    "Github" -> "https://publicURL/MyLibrary.paclet"
}]

<<MyLibrary`

This will create a local folder named wl_packages, where installed packages will be stored.

Global Installation (Classic)

Via Paclets

If the package is hosted on the Wolfram repository, then you can simply run:

PacletInstall["Username/Paclet"]

<<PacletContextName`

Or from a local paclet file:

PacletInstall["path_to_it.paclet"]

<<PacletContextName`

Namespaces

If you have conflicting symbol names or want to scope loaded package into an alias context:

Needs["PacletContextName`"->"myAlias`"]

Settings

In the settings menu you can adjust accent-colors, light/dark mode, home folder, backups and many other things related to the editing and exporting.