Excalidraw Diagram Generator

Create complete, valid .excalidraw.json files that users can directly open at excalidraw.com.

Core Capabilities

Diagram types supported:

• •Flowcharts - Process flows, decision trees, workflows
• •Architecture Diagrams - System architectures, network topologies, component diagrams
• •UML Diagrams - Class diagrams, sequence diagrams, use case diagrams
• •Mind Maps - Hierarchical concept maps, brainstorming diagrams

Two visual styles:

• •Professional Mode (default): Clean, polished diagrams for technical documentation
• •Hand-drawn Mode: Sketch-style diagrams for brainstorming and informal use

Quick Reference

JSON Schema

{
  "type": "excalidraw",
  "version": 2,
  "source": "https://excalidraw.com",
  "elements": [],
  "appState": {
    "gridSize": null,
    "viewBackgroundColor": "#ffffff"
  },
  "files": {}
}

Coordinate System

• •Origin: Top-left corner (0, 0)
• •X-axis: Increases rightward
• •Y-axis: Increases downward
• •Unit: Pixels

Grid-Based Layout System

Use a 20px grid for alignment:

GRID_UNIT = 20
COLUMN_WIDTH = 200    # Element + gap
ROW_HEIGHT = 150      # Element + gap

Position formula:
  x = START_X + (column * COLUMN_WIDTH)
  y = START_Y + (row * ROW_HEIGHT)

Recommended START_X = 50, START_Y = 100

Standard Element Sizes

Text Calculations (CRITICAL)

Text Height Formula

textHeight = fontSize × lineHeight × numberOfLines
           = fontSize × 1.25 × numberOfLines

Examples:
- 1 line, fontSize 20: 20 × 1.25 × 1 = 25px
- 3 lines, fontSize 14: 14 × 1.25 × 3 = 52.5px ≈ 53px
- 12 lines, fontSize 15: 15 × 1.25 × 12 = 225px

Text Centering Formula

text_x = shape_x + (shape_width - text_width) / 2
text_y = shape_y + (shape_height - text_height) / 2

Text Size Reference

Estimate text_width: char_count × char_width

Centering Example

Shape: x=100, y=100, width=160, height=80
Text: "Process" (7 chars), fontSize=16

text_width = 7 × 9 = 63
text_height = 1 × 20 = 20
text_x = 100 + (160 - 63) / 2 = 148.5 ≈ 148
text_y = 100 + (80 - 20) / 2 = 130

UML Class Diagram Container Height

containerHeight = headerHeight + attributesHeight + methodsHeight + padding

Where:
- headerHeight = classNameTextHeight + topPadding (typically 15px + 15px = 30px)
- attributesHeight = fontSize × 1.25 × numberOfAttributes + 10px
- methodsHeight = fontSize × 1.25 × numberOfMethods + 10px

Example (12 attributes, 10 methods, fontSize 15):
- Header: 20 + 15 = 35px
- Attributes: 15 × 1.25 × 12 + 10 = 235px
- Methods: 15 × 1.25 × 10 + 10 ≈ 198px
- Total: 35 + 10 + 235 + 10 + 198 = 488px (round to 500px)

Arrow Positioning

Horizontal Arrow (Left to Right)

From shape at (x1, y1, w1, h1) to shape at (x2, y2, w2, h2):

arrow_x = x1 + w1           # Right edge of source
arrow_y = y1 + h1/2         # Vertical center
gap = x2 - (x1 + w1)        # Space between shapes
points = [[0, 0], [gap, 0]]

Vertical Arrow (Top to Bottom)

arrow_x = x1 + w1/2         # Horizontal center
arrow_y = y1 + h1           # Bottom edge of source
gap = y2 - (y1 + h1)
points = [[0, 0], [0, gap]]

Feedback Loop (Return Arrow)

From bottom-right back to left:
  Start: (800, 400)
  points=[
    [0, 0],        # Start
    [0, 80],       # Down
    [-400, 80],    # Left
    [-400, -150]   # Up to target
  ]

Z-Order (Element Array Order)

Elements render in array order. First = back, last = front.

Correct order:

1. •Background shapes (containers, frames)
2. •Connection lines/arrows
3. •Foreground shapes (nodes, boxes)
4. •Text labels
5. •Icons/overlays

Visual Styles

Professional Mode (Default)

Use for: Architecture diagrams, UML, technical docs, formal presentations

{
  "roughness": 0,
  "fillStyle": "solid",
  "strokeWidth": 2,
  "fontFamily": 2
}

Colors (light backgrounds for readability):

Hand-drawn Mode

Use for: Brainstorming, sketches, informal sharing

{
  "roughness": 1,
  "fillStyle": "hachure",
  "strokeWidth": 2,
  "fontFamily": 1
}

Colors (medium saturation):

Stroke color: #1e1e1e (dark gray, softer than pure black)

Element Types

Common Properties (required for all)

{
  "id": "unique-id",
  "type": "rectangle",
  "x": 100,
  "y": 100,
  "width": 160,
  "height": 80,
  "strokeColor": "#1e1e1e",
  "backgroundColor": "transparent",
  "fillStyle": "solid",
  "strokeWidth": 2,
  "roughness": 1,
  "opacity": 100,
  "angle": 0,
  "seed": 100,
  "version": 1,
  "isDeleted": false,
  "boundElements": null,
  "link": null,
  "locked": false
}

Type-Specific Properties

Rectangle: Add "roundness": {"type": 3} for rounded corners

Text:

{
  "type": "text",
  "text": "Content\nLine 2",
  "fontSize": 16,
  "fontFamily": 1,
  "textAlign": "center",
  "verticalAlign": "middle"
}

• •fontFamily: 1=Virgil (hand), 2=Helvetica, 3=Cascadia (mono)

Arrow/Line:

{
  "type": "arrow",
  "points": [[0, 0], [100, 0]],
  "startArrowhead": null,
  "endArrowhead": "arrow"
}

• •Points are relative to element's x,y
• •Arrowheads: null, "arrow", "bar", "dot", "triangle"

Workflow

Step 1: Identify Diagram Type

Match the request to a diagram type:

• •Flowchart: Process flows, algorithms, decision trees, workflows
• •Architecture: System designs, microservices, cloud infrastructure
• •UML Class: Object-oriented design, class hierarchies, relationships
• •Mind Map: Brainstorming, concept hierarchies, topic exploration

Step 2: Use Templates as Foundation

Templates in assets/:

• •flowchart-template.json
• •architecture-template.json
• •uml-class-template.json
• •mindmap-template.json

Usage:

1. •Read the appropriate template
2. •Modify IDs, text, positions, colors
3. •Add/remove elements as needed
4. •Ensure all IDs are unique

Step 3: Generate Elements

Key element types:

• •rectangle - Boxes, containers, processes
• •ellipse - Start/end nodes, databases
• •diamond - Decisions, conditional branches
• •arrow / line - Connections, flows
• •text - Labels, descriptions

Step 4: Calculate Layout

Use the grid system and text centering formulas above.

Layout strategies:

• •Flowcharts: Top-to-bottom, centered alignment
• •Architecture: Left-to-right for flow, grouped by layer
• •UML Class: Use container height formula; prevent text overflow
• •Mind Maps: Radial from center, balanced branches

Step 5: Style and Polish

1. •Choose visual style (Professional or Hand-drawn)
2. •Apply consistent colors from the palette
3. •Ensure adequate spacing (80-100px between elements)

Step 6: Save to File

Always save directly as .excalidraw.json (no code blocks).

1. •Write complete JSON to file
2. •Name descriptively (e.g., user-login-flow.excalidraw.json)
3. •Save to current directory unless specified otherwise

After saving, provide:

1. •Confirmation with file path
2. •Brief description of diagram structure
3. •Instructions: "Open at excalidraw.com → Menu → Open"

Common Patterns

Pattern 1: Sequential Flow

For A → B → C processes:

1. •Place elements vertically with 120px gaps
2. •Use rectangles for processes, ellipses for start/end
3. •Connect with arrows (endArrowhead: "arrow")
4. •Center-align all elements

Pattern 2: Decision Tree

For conditional branches:

1. •Use diamond for decision nodes
2. •Branch arrows left/right or up/down
3. •Add text labels on arrows ("Yes", "No")
4. •Rejoin paths when appropriate

Pattern 3: Hierarchical Structure

For layered architectures:

1. •Group elements by layer (horizontal rows)
2. •Use different colors per layer
3. •Vertical arrows show dependencies
4. •Consistent element sizes within layers

Pattern 4: Radial Mind Map

For concept exploration:

1. •Central node (ellipse) in middle
2. •Lines radiate outward
3. •Different colors per branch
4. •Rectangles for sub-topics

Positioning Checklist

Before generating:

1. •Define grid: START_X, START_Y, COLUMN_WIDTH, ROW_HEIGHT
2. •List all elements with row/column positions
3. •Calculate exact x,y using formulas
4. •Calculate text positions using centering formula
5. •Calculate arrow start points and relative endpoints
6. •Order elements correctly for z-order
7. •Assign unique IDs and incrementing seeds

Complete Node Example

[
  {
    "id": "node1-box",
    "type": "rectangle",
    "x": 100, "y": 100, "width": 160, "height": 80,
    "strokeColor": "#1971c2",
    "backgroundColor": "#a5d8ff",
    "fillStyle": "solid",
    "strokeWidth": 2,
    "roughness": 1,
    "opacity": 100,
    "angle": 0,
    "seed": 100,
    "version": 1,
    "isDeleted": false,
    "boundElements": [{"id": "arrow1", "type": "arrow"}],
    "roundness": {"type": 3},
    "link": null,
    "locked": false
  },
  {
    "id": "node1-text",
    "type": "text",
    "x": 130, "y": 130,
    "width": 100, "height": 20,
    "text": "Process Step",
    "fontSize": 16,
    "fontFamily": 1,
    "textAlign": "center",
    "verticalAlign": "middle",
    "strokeColor": "#1e1e1e",
    "backgroundColor": "transparent",
    "fillStyle": "solid",
    "strokeWidth": 1,
    "roughness": 1,
    "opacity": 100,
    "angle": 0,
    "seed": 101,
    "version": 1,
    "isDeleted": false,
    "boundElements": null,
    "link": null,
    "locked": false
  }
]

Tips for Quality Diagrams

1. •Unique IDs: Generate random 8-16 character IDs for each element
2. •Consistent spacing: Follow spacing guidelines strictly
3. •Color harmony: Use the recommended color palette
4. •Text sizing: Match text width to container width with padding
5. •Arrow connections: Position arrow start/end points precisely
6. •Version numbers: Use random integers for versionNonce and seed

Handling Complex Requests

For large or complex diagrams:

1. •Start simple: Create core structure first
2. •Iterate: Add details progressively
3. •Group logically: Use visual grouping (colors, spacing)
4. •Limit complexity: Suggest breaking into multiple diagrams if needed
5. •Maintain readability: Ensure text doesn't overlap, adequate spacing

Resources

assets/

Templates for common diagram types:

• •flowchart-template.json
• •architecture-template.json
• •uml-class-template.json
• •mindmap-template.json

references/

• •excalidraw-format.md - Complete JSON format specification
• •elements.md - Element types and properties
• •processing-loop-template.md - Processing loop example