meraid

Render Mermaid diagrams in your terminal or Rust application.

Features

• Pure Rust implementation — Zero external dependencies, blazing fast, fully portable
• AI-friendly — JSON output mode for programmatic parsing, perfect for AI coding agents
• 5+ diagram types — Flowcharts, sequence diagrams, class diagrams, state diagrams, pie charts
• 6 color themes — default, terra, neon, mono, amber, phosphor
• ASCII fallback — Works on any terminal, even the most basic ones
• Pipe-friendly CLI — cat diagram.mmd | meraid just works

Why Meraid?

Mermaid is excellent for documentation, but rendering it typically requires a browser or external service. Meraid brings Mermaid rendering directly to your terminal — perfect for SSH sessions, CI logs, TUI applications, or any environment with Rust.

Built with love for the Rust ecosystem, providing a fast, dependency-free alternative to existing solutions.

Install

From Git (Recommended - Latest)

cargo install --git https://github.com/Binlogo/meraid.git

From Source

git clone https://github.com/Binlogo/meraid.git
cd meraid
cargo build --release
cargo install --path .

From Crates.io (Coming Soon)

cargo install meraid

With Homebrew (coming soon)

brew install meraid

Quick Start

CLI

# Render from file
meraid diagram.mmd

# Render from stdin
echo "graph LR; A-->B-->C" | meraid

# Use a theme
meraid diagram.mmd --theme neon

# ASCII-only output
meraid diagram.mmd --ascii

# JSON output (AI-friendly)
meraid diagram.mmd --format json

Rust Library

use meraid::{render, ThemeType};

fn main() {
    let diagram = render("graph LR\n  A --> B --> C", ThemeType::Default).unwrap();
    println!("{}", diagram);
}

Supported Diagram Types

Flowcharts

All directions supported: LR, RL, TD/TB, BT.

graph TD
    A[Start] --> B{Is valid?}
    B -->|Yes| C(Process)
    C --> D([Done])
    B -->|No| E[Error]

┌─────────────┐
│             │
│    Start    │
│             │
└──────┬──────┘
       │
       ▼
┌──────◇──────┐
│             │
│  Is valid?  │
│             │
└──────◇──────┘
       │
       ╰──────────────────╮
    Yes│                  │No
       ▼                  ▼
╭─────────────╮    ┌─────────────┐
│             │    │             │
│   Process   │    │    Error    │
│             │    │             │
╰──────┬──────╯    └─────────────┘
       │
       ▼
╭─────────────╮
(             )
(    Done     )
(             )
╰─────────────╯

Node shapes: rectangle [text], rounded (text), diamond {text}, stadium ([text]), subroutine [[text]]

Edge styles: solid -->, dotted -.->, thick ==>, labeled -->|text|

Sequence Diagrams

sequenceDiagram
    Alice->>Bob: Hello Bob
    Bob-->>Alice: Hi Alice
    Alice->>Bob: How are you?
    Bob-->>Alice: Great!

 ┌──────────┐      ┌──────────┐
 │  Alice   │      │   Bob    │
 └──────────┘      └──────────┘
      ┆ Hello Bob       ┆
      ──────────────────►
      ┆ Hi Alice        ┆
      ◄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄
      ┆ How are you?    ┆
      ──────────────────►
      ┆ Great!          ┆
      ◄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄

Message types: solid arrow ->>, dashed arrow -->>

Participants: participant, actor, aliases

Class Diagrams

classDiagram
    class Animal {
        +String name
        +int age
        +makeSound()
    }
    class Dog {
        +String breed
        +fetch()
    }
    Animal <|-- Dog

  ┌──────────────┐
  │    Animal    │
  ├──────────────┤
  │ +String name │
  │ +int age     │
  ├──────────────┤
  │ +makeSound() │
  └──────────────┘
          △
          │
  ┌───────────────┐
  │      Dog      │
  ├───────────────┤
  │ +String breed │
  ├───────────────┤
  │ +fetch()      │
  └───────────────┘

Relationships: inheritance <|--, composition *--, aggregation o--, association --

Members: attributes and methods with visibility (+ public, - private, # protected)

State Diagrams

stateDiagram-v2
    [*] --> Idle
    Idle --> Processing: start
    Processing --> Done: complete
    Done --> [*]

╭───────◯──────╮
│              │
│      ●       │
│              │
╰───────◯──────╯
        │
        ▼
╭──────────────╮
│              │
│     Idle     │
│              │
╰───────┬──────╯
        │
   start│
        ▼
╭──────────────╮
│              │
│  Processing  │
│              │
╰───────┬──────╯
        │
complete│
        ▼
╭──────────────╮
│              │
│     Done     │
│              │
╰───────┬──────╯
        │
        ▼
╭───────◯──────╮
│              │
│      ◉       │
│              │
╰───────◯──────╯

Features: [*] start/end states, transition labels, composite states

Pie Charts

pie title Pets adopted by volunteers
    "Dogs" : 386
    "Cats" : 85
    "Rats" : 15

  Dogs┃████████████████████████████████  79.4%
  Cats┃▓▓▓▓▓▓▓  17.5%
  Rats┃░   3.1%

ER Diagrams

erDiagram
    CUSTOMER {
        int id PK
        string name
        string email
    }
    ORDER {
        int id PK
        int customer_id FK
        date order_date
    }
    CUSTOMER ||--o{ ORDER : places

  ┌────────────────────┐
  │      CUSTOMER      │
  ├────────────────────┤
  │PK    : id          │
  │      : name        │
  │      : email       │
  └────────────────────┘
  
  ┌────────────────────┐
  │       ORDER        │
  ├────────────────────┤
  │PK    : id          │
  │   FK : customer_id │
  │      : order_date  │
  └────────────────────┘
  
  CUSTOMER ||--o{ ORDER

Cardinality notation:

• || exactly one
• }| one or more
• o| zero or one
• o{ zero or more

Attribute markers:

• PK primary key
• FK foreign key

CLI Options

Themes

6 built-in themes:

Roadmap

• ER diagrams ✅
• Block diagrams
• Git graphs
• Treemaps
• Mindmaps
• More themes (gruvbox, monokai, dracula, nord, solarized)
• Auto-fit to terminal width
• Interactive TUI viewer

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

Acknowledgements

Inspired by termaid by fasouto.

License

MIT License — see LICENSE for details.

Made with ❤️ in Rust