FreeFlowCharts API

Free public API for creating, exporting, and sharing interactive flowcharts, Venn diagrams, org charts, pie charts, and mind maps. No API key required.

Live app: freeflowcharts.app API docs page: freeflowcharts.app/api-docs OpenAPI spec: freeflowcharts.app/openapi.json

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Quick Start

Create a flowchart in one request:

curl -X POST https://freeflowcharts.app/api/create-flowchart \
  -H "Content-Type: application/json" \
  -d '{
    "title": "My Flow",
    "createdBy": "My Agent",
    "nodes": [
      { "id": "1", "type": "start", "label": "Begin" },
      { "id": "2", "type": "process", "label": "Do work" },
      { "id": "3", "type": "decision", "label": "Done?" },
      { "id": "4", "type": "end", "label": "Finish" }
    ],
    "edges": [
      { "from": "1", "to": "2" },
      { "from": "2", "to": "3" },
      { "from": "3", "to": "4", "label": "Yes" },
      { "from": "3", "to": "2", "label": "No" }
    ],
    "theme": "neon"
  }'

Response:

{
  "success": true,
  "flowId": "abc123",
  "shareId": "k7Rm2xP9qWnE",
  "url": "https://freeflowcharts.app/view/k7Rm2xP9qWnE",
  "embed": "<iframe src=\"https://freeflowcharts.app/view/k7Rm2xP9qWnE\" width=\"800\" height=\"600\" frameborder=\"0\"></iframe>",
  "branding": "Powered by FreeFlowCharts — https://freeflowcharts.app"
}

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Endpoints

Flowchart

Method	Endpoint	Description
POST	/api/create-flowchart	Create a flowchart and get a shareable link
GET	/api/export/json?id=<shareId>	Export as structured JSON
GET	/api/export/mermaid?id=<shareId>	Export as Mermaid syntax (text/plain)
GET	/api/export/svg?id=<shareId>	Export as SVG image (image/svg+xml)
GET	/api/export/png?id=<shareId>	Export as PNG image (image/png, 1600px wide)

Venn Diagram

Method	Endpoint	Description
POST	/api/create-venn	Create a Venn diagram and get a shareable link
GET	/api/export-venn/json?id=<shareId>	Export as JSON
GET	/api/export-venn/svg?id=<shareId>	Export as SVG

Org Chart

Method	Endpoint	Description
POST	/api/create-orgchart	Create an org chart (tree hierarchy)
GET	/api/export-orgchart/json?id=<shareId>	Export as JSON
GET	/api/export-orgchart/svg?id=<shareId>	Export as SVG

Pie Chart

Method	Endpoint	Description
POST	/api/create-piechart	Create a pie/donut chart
GET	/api/export-piechart/json?id=<shareId>	Export as JSON
GET	/api/export-piechart/svg?id=<shareId>	Export as SVG

Mind Map

Method	Endpoint	Description
POST	/api/create-mindmap	Create a mind map (radial layout)
GET	/api/export-mindmap/json?id=<shareId>	Export as JSON
GET	/api/export-mindmap/svg?id=<shareId>	Export as SVG

Utility

Method	Endpoint	Description
GET	/api/node-types	List all 19 supported node types
GET	/api/health	API status and endpoint listing

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Create Flowchart — Request Body

Field	Type	Required	Description
title	string	Yes	Flowchart title (max 200 chars)
description	string	No	Description (max 1000 chars)
createdBy	string	No	Attribution (e.g. "ChatGPT", "My Agent")
nodes	array	Yes	Array of node objects (1–100)
nodes[].id	string	Yes	Unique node ID
nodes[].type	string	No	Node type (default: "process") — see Node Types
nodes[].label	string	Yes	Display label (max 200 chars)
nodes[].description	string	No	Node description (max 500 chars)
nodes[].x	number	No	X position (if omitted, uses intelligent hierarchical tree layout via Dagre)
nodes[].y	number	No	Y position (if omitted, uses intelligent hierarchical tree layout via Dagre)
edges	array	Yes	Array of edge objects (0–200)
edges[].from	string	Yes	Source node ID
edges[].to	string	Yes	Target node ID
edges[].label	string	No	Edge label (max 100 chars)
background	string	No	Hex color (#1a1a2e) or CSS linear-gradient(...). Default: #06040d
theme	string	No	Visual theme — see Themes

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Export Endpoints

All export endpoints accept optional query parameters:

Param	Description
id	(required) The shareId returned when the flowchart was created
bg	Override background color/gradient for this export
theme	Override visual theme for this export

Priority: ?bg= override > stored background > theme background > default (#06040d) Priority: ?theme= override > stored theme > "default"

JSON Export

The JSON export includes both stored and resolved values:

Field	Description
theme	Stored theme (what was saved at creation)
background	Stored background (what was saved at creation)
resolvedTheme	Effective theme after ?theme= override
resolvedBackground	Effective background after ?bg= / theme resolution
availableThemes	Array of all valid theme names

Examples

# Export as Mermaid syntax
curl "https://freeflowcharts.app/api/export/mermaid?id=YOUR_SHARE_ID"

# Export as SVG
curl "https://freeflowcharts.app/api/export/svg?id=YOUR_SHARE_ID" -o flow.svg

# Export as PNG
curl "https://freeflowcharts.app/api/export/png?id=YOUR_SHARE_ID" -o flow.png

# Override background on export
curl "https://freeflowcharts.app/api/export/svg?id=YOUR_SHARE_ID&bg=%231a1a2e" -o custom.svg

# Override theme on export
curl "https://freeflowcharts.app/api/export/png?id=YOUR_SHARE_ID&theme=candy" -o candy.png

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Error Codes

Status	Meaning
400	Missing/invalid fields, duplicate node IDs, or dangling edge references
404	Flowchart not found (export)
405	Wrong HTTP method
429	Rate limit exceeded (30/hr per IP)
500	Internal server error

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Rate Limits

• 30 requests per hour per IP address
• Applies to both create and export endpoints
• No API key or authentication required

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Theme Previews

All 7 themes applied to the same flowchart:

Default	Neon	Pastel

Retro	Ocean	Brutalist

Candy

See THEMES.md for full descriptions and usage details.

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Org Chart — Quick Example

curl -X POST https://freeflowcharts.app/api/create-orgchart \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Engineering",
    "nodes": [
      { "id": "1", "label": "VP Engineering", "title": "Vice President" },
      { "id": "2", "label": "Frontend Lead", "parentId": "1" },
      { "id": "3", "label": "Backend Lead", "parentId": "1" },
      { "id": "4", "label": "Dev A", "parentId": "2" },
      { "id": "5", "label": "Dev B", "parentId": "3" }
    ]
  }'

Max 100 nodes. Auto-layout tree. Colors assigned by depth.

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Pie Chart — Quick Example

curl -X POST https://freeflowcharts.app/api/create-piechart \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Market Share",
    "slices": [
      { "label": "Product A", "value": 40 },
      { "label": "Product B", "value": 30 },
      { "label": "Other", "value": 30 }
    ],
    "donut": true
  }'

Max 50 slices. Optional donut mode. Colors auto-assigned.

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Mind Map — Quick Example

curl -X POST https://freeflowcharts.app/api/create-mindmap \
  -H "Content-Type: application/json" \
  -d '{
    "title": "Project Ideas",
    "nodes": [
      { "id": "1", "label": "Main Topic" },
      { "id": "2", "label": "Branch A", "parentId": "1" },
      { "id": "3", "label": "Branch B", "parentId": "1" },
      { "id": "4", "label": "Sub-idea", "parentId": "2" }
    ]
  }'

Max 100 nodes. Auto radial layout. Colors assigned by branch.

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Further Reading

• Node Types — All 19 node types with colors and descriptions
• Themes — Visual theme guide with descriptions
• OpenAPI Spec — Machine-readable API specification
• Agent Skill File — Packaged skill for AI agents
• Examples — Code examples in bash, Python, and JavaScript

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Links

Resource	URL
Live app	https://freeflowcharts.app
API docs page	https://freeflowcharts.app/api-docs
OpenAPI spec	https://freeflowcharts.app/openapi.json
Skill file	https://freeflowcharts.app/SKILL.md
LLM info	https://freeflowcharts.app/llms.txt
API repo (GitHub)	https://github.com/nerdfreakuser/freeflowcharts-api

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Built by FreeFlowCharts — free flowchart maker with AI