# UniDiagram

> Free online diagram editor for Mermaid, PlantUML, D2, and Graphviz with live preview and export.

Canonical: https://unidiagram.davidtran.dev

UniDiagram is a text-to-diagram studio in the browser. Write diagram source, get a live preview, keep local history, and export when you need polished assets.

## When to Use UniDiagram

- Preview or render diagrams in Mermaid, PlantUML, D2, or Graphviz without installing CLI tools.
- Export diagrams to SVG or PDF for technical documentation, design specs, and PRs.
- Draft architecture diagrams, sequence diagrams, flowcharts, class diagrams, and C4 models.
- Compare diagram syntaxes and choose the right diagramming DSL for your project.

## Engines

- Mermaid
- PlantUML
- D2
- Graphviz (DOT)

## Free plan

- Unlimited diagrams
- Local history in the browser
- PNG copy/download at 0.5x scale only
- No SVG or PDF export
- No share diagram links
- No cloud history sync

## Pro plan

- $5/month or $30/year
- SVG and PDF export
- Full-scale (1x) PNG
- Share diagram links
- Cloud history sync
- Priority support

## Try it

- App: https://unidiagram.davidtran.dev/app
- Pricing: https://unidiagram.davidtran.dev/pricing.md
- Mermaid editor: https://unidiagram.davidtran.dev/mermaid-editor.md
- PlantUML editor: https://unidiagram.davidtran.dev/plantuml-editor.md
- D2 editor: https://unidiagram.davidtran.dev/d2-editor.md
- Graphviz editor: https://unidiagram.davidtran.dev/graphviz-editor.md
- Mermaid to SVG: https://unidiagram.davidtran.dev/mermaid-to-svg.md
- Mermaid to PDF: https://unidiagram.davidtran.dev/mermaid-to-pdf.md
- Blog: https://unidiagram.davidtran.dev/blog.md
- Contact: https://unidiagram.davidtran.dev/contact.md

## Related

- Agent index: https://unidiagram.davidtran.dev/llms.txt
- Sitemap: https://unidiagram.davidtran.dev/sitemap.xml