Excalidraw

Excalidraw Diagrams

Create hand-drawn style diagrams, flowcharts, architecture diagrams, and mind maps using the Excalidraw format. Diagrams are rendered interactively in the Canvas panel.

When to Use This Skill

Use create_excalidraw_diagram when the user wants to visualize structure, flow, or relationships — not raw numbers.

Diagram Type

Choose based on user intent. For Swimlane, Class, Sequence, ER, and DFD diagrams, read diagram-patterns.md before generating.

Available Tools

• create_excalidraw_diagram(elements, title, background_color): Generate a diagram from Excalidraw element JSON

Color Palette

Use these colors consistently across all diagrams.

Primary Colors (strokes, arrows, text)

Fill Colors (shape backgrounds)

Background Zone Colors (use with opacity: 35 for layer grouping)

Element Format

Required Fields (all elements)

type, id (unique string), x, y, width, height

Defaults (skip if using these values)

strokeColor="#1e1e1e", backgroundColor="transparent", fillStyle="solid", strokeWidth=2, roughness=1, opacity=100

Shape Types

Rectangle

{ "type": "rectangle", "id": "r1", "x": 100, "y": 100, "width": 200, "height": 80,
  "roundness": { "type": 3 }, "backgroundColor": "#a5d8ff", "fillStyle": "solid" }

• roundness: { type: 3 } for rounded corners

Ellipse

{ "type": "ellipse", "id": "e1", "x": 100, "y": 100, "width": 150, "height": 150 }

Diamond

{ "type": "diamond", "id": "d1", "x": 100, "y": 100, "width": 150, "height": 150 }

Label on shape (PREFERRED — no separate text element needed)

{ "type": "rectangle", "id": "r1", "x": 100, "y": 100, "width": 200, "height": 80,
  "label": { "text": "My Label", "fontSize": 20 } }

• Works on rectangle, ellipse, diamond
• Text auto-centers; container auto-resizes to fit
• Also works on arrows: "label": { "text": "connects" }

Standalone Text (titles, annotations only)

{ "type": "text", "id": "t1", "x": 150, "y": 50, "text": "Title", "fontSize": 24 }

• x is the LEFT edge. To center at position cx: set x = cx - text.length × fontSize × 0.25

Arrow

{ "type": "arrow", "id": "a1", "x": 300, "y": 150, "width": 150, "height": 0,
  "points": [[0,0],[150,0]], "endArrowhead": "arrow",
  "startBinding": { "elementId": "r1", "fixedPoint": [1, 0.5] },
  "endBinding": { "elementId": "r2", "fixedPoint": [0, 0.5] } }

• points: [dx, dy] offsets from element x, y
• endArrowhead: null | "arrow" | "bar" | "dot" | "triangle"
• strokeStyle: "solid" | "dashed" | "dotted"
• fixedPoint for bindings: top [0.5,0], bottom [0.5,1], left [0,0.5], right [1,0.5]

Pseudo-Elements (not drawn — control behavior)

cameraUpdate — sets the viewport

{ "type": "cameraUpdate", "width": 800, "height": 600, "x": 0, "y": 0 }

• x, y: top-left corner of visible area (scene coordinates)
• Must be 4:3 ratio: 400×300, 600×450, 800×600, 1200×900, 1600×1200
• ALWAYS place a cameraUpdate as the first element to frame the diagram
• No id needed

delete — removes elements by ID

{ "type": "delete", "ids": "r1,a1,t2" }

• Comma-separated element IDs to remove
• Use when updating an existing diagram to remove elements before adding replacements
• Never reuse a deleted ID — assign new IDs to replacements

Camera Sizing Guide

The diagram displays at ~700px width. Use these standard sizes:

Font size rules:

• Body text / labels: minimum 16
• Titles / headings: minimum 20
• Annotations: minimum 14 (use sparingly)
• At XL/XXL camera: increase minimums by ~4px

Element sizing rules:

• Labeled rectangles/ellipses: minimum 120 × 60
• Leave 20–30px gaps between elements

Updating an Existing Diagram

When the user asks to modify a diagram, you will receive the current elements in context. Respond with the complete updated elements array:

• Keep the same id for unchanged elements
• Modify fields on elements you want to change
• Omit elements you want to remove
• Add new elements with unique IDs not used before

Example: Flowchart

[
  { "type": "cameraUpdate", "width": 800, "height": 600, "x": 0, "y": 0 },
  { "type": "rectangle", "id": "el-1",
    "x": 300, "y": 60, "width": 160, "height": 60,
    "strokeColor": "#4a9eed", "backgroundColor": "#a5d8ff",
    "fillStyle": "solid", "roundness": { "type": 3 },
    "label": { "text": "Start", "fontSize": 18 } },
  { "type": "diamond", "id": "el-2",
    "x": 280, "y": 170, "width": 200, "height": 90,
    "strokeColor": "#f59e0b", "backgroundColor": "#fff3bf",
    "fillStyle": "solid",
    "label": { "text": "Decision?", "fontSize": 16 } },
  { "type": "arrow", "id": "el-3",
    "x": 380, "y": 120, "width": 0, "height": 50,
    "points": [[0,0],[0,50]], "endArrowhead": "arrow",
    "startBinding": { "elementId": "el-1", "fixedPoint": [0.5, 1] },
    "endBinding": { "elementId": "el-2", "fixedPoint": [0.5, 0] } },
  { "type": "rectangle", "id": "el-4",
    "x": 300, "y": 320, "width": 160, "height": 60,
    "strokeColor": "#22c55e", "backgroundColor": "#b2f2bb",
    "fillStyle": "solid", "roundness": { "type": 3 },
    "label": { "text": "End", "fontSize": 18 } },
  { "type": "arrow", "id": "el-5",
    "x": 380, "y": 260, "width": 0, "height": 60,
    "points": [[0,0],[0,60]], "endArrowhead": "arrow",
    "startBinding": { "elementId": "el-2", "fixedPoint": [0.5, 1] },
    "endBinding": { "elementId": "el-4", "fixedPoint": [0.5, 0] } }
]

Common Mistakes to Avoid

• Camera must use exact 4:3 ratios — non-4:3 viewports cause distortion
• Always start with cameraUpdate — without it the viewport is unpredictable
• No comments in element arrays — elements must be valid JSON. Never add // or /* */ comments inside the array; they break JSON parsing
• Text contrast — never use light gray on white. Minimum text color on white: #757575. For text on light fills use dark variants (#15803d not #22c55e)
• Arrow labels need space — long labels overflow short arrows; keep labels short or widen arrows
• No emoji — Excalidraw's font does not render emoji
• Element overlap — check that labels, boxes, and zone overlays don't stack on each other (minimum 20px gap)
• Camera padding — leave padding inside the camera frame; don't match camera size exactly to content size

UI Guidance (from tools-config)

Element Format:

• Required: type, x, y, id
• Shapes (rectangle/ellipse/diamond): add width, height
• Arrows/lines: add width, height, points [[0,0],[dx,dy]]
• Text: add text, fontSize
• Use label field on shapes for centered text
• Connect shapes with arrow elements using points routing