PlantUML vs Mermaid: Which Tool Is Best for Sequence Diagrams in Markdown?

If you’re writing technical documentation, building API guides, or creating system architecture diagrams, you’ve likely encountered the need to create sequence diagrams using plain text.

Two of the most popular tools for this are PlantUML and Mermaid. Both convert simple code into professional diagrams, but they differ significantly in syntax, setup, and integration.

In this post, we’ll compare PlantUML vs Mermaid across key factors like ease of use, Markdown compatibility, visual quality, and ecosystem — so you can choose the right tool for your workflow.

Overview: PlantUML vs Mermaid

Feature	PlantUML	Mermaid
Language	Java-based (requires Graphviz)	JavaScript-based (runs in browser)
Syntax Style	Verbose, UML-standard	Clean, Markdown-like
Diagram Types	Full UML suite (sequence, class, activity, etc.)	Sequence, flowchart, class, ERD, gantt, pie charts
Rendering	Server-side (Java)	Client-side (JavaScript)
Markdown Support	Limited (needs plugins)	Excellent (GitHub, GitLab, Obsidian)

Syntax Comparison: Sequence Diagram

PlantUML Example

@startuml
actor User
User -> Client : Enter request
Client -> Server : HTTP request
Server -> Database : Query data
Database --> Server : Return data
Server --> Client : Send response
Client --> User : Display result
@enduml

Mermaid Example

sequenceDiagram
    participant User
    participant Client
    participant Server
    participant Database

    User->>Client: Enter request
    Client->>Server: Send HTTP request
    Server->>Database: Query data
    Database-->>Server: Return data
    Server-->>Client: Send response
    Client-->>User: Display result

Verdict: Mermaid’s syntax is more intuitive and easier to read — especially for developers already used to Markdown.

Installation & Setup

PlantUML requires:

• Java Runtime Environment (JRE)
• Graphviz (for layout rendering)
• Plugins or preprocessors for Markdown

Mermaid requires:

• No local setup for web use
• Built into GitHub, GitLab, Obsidian, and modern static site generators
• Just add the Mermaid script to enable in HTML

Winner: Mermaid wins hands-down for ease of setup and speed.

Integration with Markdown & Documentation Tools

Tool	PlantUML	Mermaid
GitHub	❌ Not supported	✅ Native support
GitLab	✅ Via integration	✅ Supported
Obsidian	✅ Plugin	✅ Built-in
Typora	✅ (with config)	✅ Built-in
Confluence	✅ Official plugin	⚠️ Third-party only

Takeaway: Mermaid is ideal for open-source and developer-focused docs. PlantUML shines in enterprise environments using Confluence.

Diagram Quality & Features

• PlantUML: Highly compliant with UML standards. Supports advanced features like lifelines, alt/else blocks, notes, and constraints.
• Mermaid: Clean, modern visuals. Supports theming (light/dark), limited interactivity, and responsive rendering.

If you need strict UML compliance, PlantUML is better. For clean, modern visuals in blogs or docs, Mermaid wins.

Ecosystem & Extensibility

PlantUML excels in:

• Generating diagrams from code comments
• Integration with Java, C#, and enterprise toolchains
• Support for non-UML diagrams (e.g., network, architecture)

Mermaid shines in:

• Developer documentation (APIs, flowcharts, gantt charts)
• Static site generators (Docusaurus, Hugo, Jekyll)
• Real-time editors like Mermaid Live Editor

Final Verdict: Who Wins?

Critera	Winner
Ease of Use	🏆 Mermaid
UML Accuracy	🏆 PlantUML
Markdown Integration	🏆 Mermaid
Enterprise Tooling (Confluence)	🏆 PlantUML
Learning Curve	🏆 Mermaid
Visual Appeal	🏆 Mermaid

Conclusion

Both PlantUML and Mermaid are powerful tools, but they serve slightly different audiences:

• Choose PlantUML if you’re in an enterprise environment, need strict UML compliance, or use Confluence/Jira.
• Choose Mermaid if you’re writing Markdown-based documentation, publishing on GitHub/GitLab, or want a modern, lightweight diagramming solution.

For most technical writers, developers, and open-source contributors in 2025, Mermaid is the go-to choice thanks to its simplicity, speed, and seamless integration with modern tools.

Pro Tip

Try the Mermaid Live Editor or PlantUML Online Server to test diagrams before embedding them in your WordPress site.