merman

Merman

Mermaid diagrams, rendered in Rust.

Parse, lay out, and render Mermaid diagrams for documentation, editor previews, reports, and applications. Merman runs headlessly: its native rendering path needs no browser or JavaScript runtime. Use it as a Rust library, a CLI, or through browser and native bindings.

Try the Playground · Quick start · Ecosystem · Documentation

Riso · Flowchart	Metro · Sequence
	Pop Art · XY Chart	Atlas · Pie

Actual Merman SVG exports from the Playground’s standalone JSON theme library. Open a design above for its gallery of diagram types, sources, editable recipe, and integration examples.

Used by Zed. Zed uses Merman as its Rust Mermaid backend. Read the merged integration.

Quick start

The examples below use 0.10.0-alpha.2. For release selection and prebuilt downloads, start with the host installation guide.

Rust

With Rust 1.95 or later, add Merman to your Cargo.toml:

[dependencies]
merman = "=0.10.0-alpha.2"

Save this as src/main.rs:

use merman::{OperationControl, RenderOutput, RenderRequest, Renderer, SvgRequest};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let output = Renderer::new().render(RenderRequest::svg(
        "flowchart LR\n  Source[Mermaid source] --> Merman --> Svg[SVG string]",
        OperationControl::new(),
        SvgRequest::default(),
    ))?;
    let RenderOutput::Svg(Some(svg)) = output else {
        return Err("no Mermaid diagram detected".into());
    };
    print!("{}", svg.svg());
    Ok(())
}

cargo run --quiet > diagram.svg

See the Rust embedding guide and runnable examples for configuration, repeated rendering, and host integration.

CLI

Install from Cargo and render a first diagram:

cargo install merman-cli --version 0.10.0-alpha.2 --locked
printf 'flowchart LR\n  Source --> Merman --> SVG\n' | merman-cli render - --output diagram.svg

For an existing file, run merman-cli render diagram.mmd --output diagram.svg. The CLI guide also covers prebuilt installation, PNG/JPEG/PDF export, Markdown batches, linting, and ASCII/Unicode output for supported families.

Ecosystem

Choose the host where your application runs. Each guide owns its installation steps and available operations; the host guide records release availability across channels.

Beyond SVG, Merman offers typed diagram models, diagnostics, editor APIs, image/PDF export, and terminal output. Start with the capability guide for feature selection or the package surface guide for the complete product map.

Make it your own

Built-in presets such as Brutalist, Spotless, Cyberpunk, and Ghibli are selected by their runtime preset IDs. The standalone explorations in the Playground theme designs are editable JSON recipes, including the four designs shown above and coordinated light/dark designs. Browse by diagram type and style, then copy a recipe to use it through Rust, CLI, Web, or Node.

The theme guide covers adopting and customizing recipes, family scope, and output support. The preset gallery shows more real renders and includes design credits.

Rendering quality and performance

Merman follows pinned Mermaid source, with checks for parsing, layout, configuration, themes, and SVG structure. Browse the alignment dashboard for diagram-family coverage and comparison evidence, from Flowchart and Sequence to Class, ER, State, Gantt, Mindmap, and charts.

Text measurement, host fonts, HTML labels, and hand-drawn paths can differ from browser output. The SVG output guide explains the output pipelines and viewer requirements. Performance methodology, workloads, and reproducible commands live in the benchmark guide.

Documentation and contributing

The documentation index routes to maintained guides for integration, architecture, and development. See resource policy for cancellation and bounded host workloads, rendering security for safe embedding, and the contributor and CI guide for local checks. Use the changelog and release and upgrade index when moving between releases.

License and attribution

Merman’s own code is available under the Apache License 2.0 or MIT License. Distributed components retain their own licenses and notices, including EPL-2.0 ELK in default Rust rendering features. See THIRD_PARTY_NOTICES.md for the feature-dependent requirements.

Merman is independent of, and not affiliated with, endorsed by, or sponsored by the Mermaid project or its maintainers.