---
name: kroki-diagram-api-98c06d88b206
description: "Generate diagrams from text via Kroki's multi-format rendering API"
metadata:
  openclaw:
    emoji: "📐"
    category: "tools"
    subcategory: "diagram"
    keywords: ["Kroki", "diagram generation", "text-to-diagram", "Graphviz", "PlantUML", "Mermaid"]
    source: "https://kroki.io/"
---

# Kroki Diagram API

## Overview

Kroki provides a unified HTTP API to render 20+ text-based diagram formats into images (SVG, PNG, PDF). It supports Mermaid, PlantUML, Graphviz, D2, BPMN, and more — all through a single endpoint. Self-hostable or use the free public instance. No authentication required. Ideal for generating research figures, architecture diagrams, and flowcharts programmatically.

## API Usage

### GET Request (URL-encoded)

```bash
# Graphviz DOT diagram
curl "https://kroki.io/graphviz/svg/digraph{A->B->C}" -o diagram.svg

# Mermaid diagram (base64-encoded)
echo "graph TD; A-->B; B-->C;" | base64 | \
  curl "https://kroki.io/mermaid/svg/$(cat -)" -o diagram.svg
```

### POST Request (Recommended)

```bash
# PlantUML sequence diagram
curl -X POST "https://kroki.io/plantuml/svg" \
  -H "Content-Type: text/plain" \
  -d '@startuml
Alice -> Bob: Hello
Bob --> Alice: Hi!
@enduml' -o sequence.svg

# Mermaid flowchart
curl -X POST "https://kroki.io/mermaid/svg" \
  -H "Content-Type: text/plain" \
  -d 'graph TD
    A[Data Collection] --> B[Preprocessing]
    B --> C[Model Training]
    C --> D[Evaluation]
    D -->|Good| E[Deploy]
    D -->|Bad| B' -o flowchart.svg

# Graphviz
curl -X POST "https://kroki.io/graphviz/svg" \
  -H "Content-Type: text/plain" \
  -d 'digraph {
    rankdir=LR
    "Raw Data" -> "Feature Extraction" -> "Model" -> "Prediction"
  }' -o pipeline.svg

# D2 diagram
curl -X POST "https://kroki.io/d2/svg" \
  -H "Content-Type: text/plain" \
  -d 'Client -> API: Request
API -> Database: Query
Database -> API: Results
API -> Client: Response' -o d2.svg
```

### URL Format

```
https://kroki.io/{diagram_type}/{output_format}/{encoded_source}

# Or POST to:
https://kroki.io/{diagram_type}/{output_format}
```

### Supported Diagram Types

| Type | Keyword | Best for |
|------|---------|----------|
| Mermaid | `mermaid` | Flowcharts, sequences, Gantt |
| PlantUML | `plantuml` | UML, sequences, class diagrams |
| Graphviz | `graphviz` | Network graphs, DAGs |
| D2 | `d2` | Modern text-to-diagram |
| Ditaa | `ditaa` | ASCII art diagrams |
| BlockDiag | `blockdiag` | Block diagrams |
| Nomnoml | `nomnoml` | UML-like diagrams |
| WaveDrom | `wavedrom` | Digital timing diagrams |
| Vega | `vega` | Data visualizations |
| Vega-Lite | `vegalite` | Simplified data viz |
| C4 PlantUML | `c4plantuml` | C4 architecture |
| BPMN | `bpmn` | Business processes |
| Bytefield | `bytefield` | Protocol/byte diagrams |
| Excalidraw | `excalidraw` | Hand-drawn style |

### Output Formats

| Format | Extension | Use case |
|--------|-----------|----------|
| SVG | `/svg` | Web, scalable |
| PNG | `/png` | Documents, slides |
| PDF | `/pdf` | Papers, print |
| JPEG | `/jpeg` | Compatibility |

## Python Usage

```python
import requests
import base64
import zlib


KROKI_URL = "https://kroki.io"


def render_diagram(source: str, diagram_type: str = "mermaid",
                   output_format: str = "svg") -> bytes:
    """Render a text diagram to image via Kroki."""
    resp = requests.post(
        f"{KROKI_URL}/{diagram_type}/{output_format}",
        headers={"Content-Type": "text/plain"},
        data=source,
    )
    resp.raise_for_status()
    return resp.content


def save_diagram(source: str, output_path: str,
                 diagram_type: str = "mermaid",
                 output_format: str = "svg"):
    """Render and save a diagram to file."""
    content = render_diagram(source, diagram_type, output_format)
    with open(output_path, "wb") as f:
        f.write(content)


def render_research_pipeline(steps: list) -> bytes:
    """Create a research pipeline flowchart."""
    nodes = []
    for i, step in enumerate(steps):
        node_id = chr(65 + i)
        nodes.append(f"    {node_id}[{step}]")
        if i > 0:
            prev_id = chr(65 + i - 1)
            nodes.append(f"    {prev_id} --> {node_id}")

    mermaid = "graph TD\n" + "\n".join(nodes)
    return render_diagram(mermaid, "mermaid", "svg")


# Example: create a research workflow diagram
workflow = """graph TD
    A[Literature Review] --> B[Hypothesis]
    B --> C[Data Collection]
    C --> D[Statistical Analysis]
    D --> E{Significant?}
    E -->|Yes| F[Write Paper]
    E -->|No| G[Revise Hypothesis]
    G --> B
    F --> H[Peer Review]"""

save_diagram(workflow, "research_workflow.svg", "mermaid")

# Example: Graphviz citation network
citation_graph = """digraph {
    rankdir=BT
    node [shape=box, style=rounded]
    "Vaswani 2017" -> "BERT 2018"
    "Vaswani 2017" -> "GPT 2018"
    "BERT 2018" -> "RoBERTa 2019"
    "GPT 2018" -> "GPT-2 2019"
    "GPT-2 2019" -> "GPT-3 2020"
}"""
save_diagram(citation_graph, "citations.svg", "graphviz")

# Example: research pipeline helper
pipeline_svg = render_research_pipeline([
    "Raw Data", "Cleaning", "Feature Engineering",
    "Model Training", "Evaluation", "Deployment"
])
```

## Self-Hosting

```bash
# Run Kroki locally via Docker
docker run -d -p 8000:8000 yuzutech/kroki

# Then use http://localhost:8000 instead of https://kroki.io
```

## References

- [Kroki](https://kroki.io/)
- [Kroki Documentation](https://docs.kroki.io/)
- [Kroki GitHub](https://github.com/yuzutech/kroki)


---
Source attribution: wentorai
Original project: https://github.com/wentorai/research-plugins/blob/bf44b3cd617fa94c8a1b254c5d1987142ca3d631/skills/tools/diagram/kroki-diagram-api/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2026 Wentor AI

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: wentorai
Original project: https://github.com/wentorai/research-plugins/blob/bf44b3cd617fa94c8a1b254c5d1987142ca3d631/skills/tools/diagram/kroki-diagram-api/SKILL.md
Attribution basis: Source repository record

Fields of work: Data & Analytics, Design, Product Management
Roles: Data Analyst, Product Manager, UX Designer
Specialties: API
Tools: Kroki
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: a6ba090fe73e208ef5f804fbbee473a58b1b638d4184d407b5211ce5b0779f3a