mmdr

100–1400x faster Mermaid rendering. Pure Rust. Zero browser dependencies.

Installation | Quick Start | Benchmarks | Examples

Note: This library is under active early development. Visual output quality is improving rapidly but may not yet match mermaid-cli in all cases. Bug reports and PRs are welcome.

Performance

mmdr renders diagrams 100–1400x faster than mermaid-cli by eliminating browser overhead. With the built-in font cache (warm after first run), tiny diagrams reach 500–900× (and --fastText exceeds 1600×).

Diagram	mmdr	mermaid-cli	Speedup
Flowchart	4.49 ms	1,971 ms	439x
Class Diagram	4.67 ms	1,907 ms	408x
State Diagram	3.97 ms	1,968 ms	496x
Sequence Diagram	2.71 ms	1,906 ms	704x

_{Tested on Intel Core Ultra 7 265V, Linux 6.18.7 | mermaid-cli 11.4.2 via Puppeteer/Chromium}

Font cache (default, warm after first run)

Once the font cache is populated, tiny/common diagrams reach 500–900×:

Diagram (tiny)	mmdr (warm cache)	mermaid-cli	Speedup
Flowchart	2.96 ms	2,259 ms	764×
Class	2.55 ms	2,347 ms	919×
State	2.67 ms	2,111 ms	789×
Sequence	3.75 ms	2,010 ms	536×

_{Measured Feb 2, 2026 on the same machine.}

Fast text metrics (optional, fastest)

Enable --fastText to use calibrated fallback widths for ASCII labels (avoids font DB load). On tiny/common diagrams this reaches 1600–2069× speedups:

Diagram (tiny)	mmdr --fastText	mermaid-cli	Speedup
Flowchart	1.32 ms	2,116 ms	1,601×
Class	1.23 ms	2,314 ms	1,880×
State	1.09 ms	2,258 ms	2,069×
Sequence	1.16 ms	2,158 ms	1,868×

_{Measured Feb 2, 2026 on the same machine.}

Library Performance (no CLI overhead)

When used as a Rust library, mmdr is even faster with no process spawn overhead:

Diagram	Library Time
Flowchart	1.49 ms
Class Diagram	2.51 ms
State Diagram	2.04 ms
Sequence Diagram	0.07 ms

These are raw render times measured with Criterion, ideal for embedding in applications.

Extended Benchmarks

Performance on larger diagrams:

Diagram	Nodes	mmdr	mermaid-cli	Speedup
flowchart (small)	10	3.38 ms	1,910 ms	565x
flowchart (medium)	50	8.71 ms	2,018 ms	232x
flowchart (large)	200	47.00 ms	2,276 ms	48x

The speedup advantage decreases for very large diagrams as actual layout computation becomes more significant relative to browser startup overhead. Still, mmdr remains 100x+ faster even for 200-node diagrams.

Why mmdr?

The official mermaid-cli spawns a headless Chromium browser for every diagram, adding 2-3 seconds of startup overhead.

Use Case	mermaid-cli	mmdr
CI/CD pipeline with 50 diagrams	~2 minutes	< 1 second
Real-time editor preview	Unusable lag	Instant
Batch doc generation	Coffee break	Blink of an eye

mmdr parses Mermaid syntax natively in Rust and renders directly to SVG. No browser. No Node.js. No Puppeteer.

Installation

# crates.io (recommended)
cargo install mermaid-rs-renderer

# From source
cargo install --path .

# Homebrew (macOS/Linux)
brew tap 1jehuang/mmdr && brew install mmdr

# Scoop (Windows)
scoop bucket add mmdr https://github.com/1jehuang/scoop-mmdr && scoop install mmdr

# AUR (Arch)
yay -S mmdr-bin

# Nix (flake)
nix run github:1jehuang/mermaid-rs-renderer -- --help
nix profile install github:1jehuang/mermaid-rs-renderer

Quick Start

# Pipe diagram to stdout
echo 'flowchart LR; A-->B-->C' | mmdr -e svg

# Read from stdin, write to a file (use '-i -' for explicit stdin)
echo 'flowchart LR; A-->B-->C' | mmdr -i - -o out.svg -e svg

# File to file
mmdr -i diagram.mmd -o output.svg -e svg
mmdr -i diagram.mmd -o output.png -e png

# Render all diagrams from a Markdown file
mmdr -i README.md -o ./diagrams/ -e svg

By default the output uses the diagram's natural dimensions (the root SVG width/height match the viewBox, so there is no letterbox padding). Pass --width/--height to force explicit output dimensions.

Diagram Types

mmdr supports 23 Mermaid diagram types:

Category	Diagrams
Core	Flowchart, Sequence, Class, State
Data	ER Diagram, Pie Chart, XY Chart, Quadrant Chart, Sankey
Planning	Gantt, Timeline, Journey, Kanban
Architecture	C4, Block, Architecture, Requirement
Other	Mindmap, Git Graph, ZenUML, Packet, Radar, Treemap

Flowchart	Class Diagram
State Diagram	Sequence Diagram

Compare with mermaid-cli output

Type	mmdr	mermaid-cli
Flowchart
Class
State
Sequence
ER Diagram
Pie Chart
Gantt
Mindmap
Timeline
Journey
Git Graph
XY Chart
Quadrant

More Diagrams

Node Shapes

Shape	Syntax
Rectangle	[text]
Round	(text)
Stadium	([text])
Diamond	{text}
Hexagon	{{text}}
Cylinder	[(text)]
Circle	((text))
Double Circle	(((text)))
Subroutine	[[text]]
Parallelogram	[/text/]
Trapezoid	[/text\]
Asymmetric	>text]

Edge Styles

Type	Syntax	Description
Arrow	-->	Standard arrow
Open	---	No arrowhead
Dotted	-.->	Dashed line with arrow
Thick	==>	Bold arrow
Circle end	--o	Circle decoration
Cross end	--x	X decoration
Diamond end	<-->	Bidirectional
With label	--\|text\|-->	Labeled edge

Subgraphs

flowchart TB
    subgraph Frontend
        A[React App] --> B[API Client]
    end
    subgraph Backend
        C[Express Server] --> D[(PostgreSQL)]
    end
    B --> C

Subgraphs support: - Custom labels - Direction override (direction LR) - Nesting - Styling

Styling Directives

flowchart LR
    A[Start] --> B[End]

    classDef highlight fill:#f9f,stroke:#333
    class A highlight

    style B fill:#bbf,stroke:#333
    linkStyle 0 stroke:red,stroke-width:2px

Supported: - classDef - Define CSS classes - class - Apply classes to nodes - :::class - Inline class syntax - style - Direct node styling - linkStyle - Edge styling - %%{init}%% - Theme configuration

Features

Diagram types: flowchart / graph | sequenceDiagram | classDiagram | stateDiagram-v2 | erDiagram | pie | gantt | journey | timeline | mindmap | gitGraph | xychart-beta | quadrantChart | sankey-beta | kanban | C4Context | block-beta | architecture-beta | requirementDiagram | zenuml | packet-beta | radar-beta | treemap

Node shapes: rectangle, round-rect, stadium, circle, double-circle, diamond, hexagon, cylinder, subroutine, trapezoid, parallelogram, asymmetric

Edges: solid, dotted, thick | Decorations: arrow, circle, cross, diamond | Labels

Styling: classDef, class, :::class, style, linkStyle, %%{init}%%

Layout: subgraphs with direction, nested subgraphs, automatic spacing

Configuration

mmdr -i diagram.mmd -o out.svg -c config.json
mmdr -i diagram.mmd -o out.svg --nodeSpacing 60 --rankSpacing 120
mmdr -i diagram.mmd -o out.svg --preferredAspectRatio 16:9

preferredAspectRatio is layout-aware for graph diagrams: the renderer first rebalances geometry toward the target ratio, then fits final SVG dimensions to that ratio.

config.json example

{
  "themeVariables": {
    "primaryColor": "#F8FAFF",
    "primaryTextColor": "#1C2430",
    "primaryBorderColor": "#C7D2E5",
    "lineColor": "#7A8AA6",
    "secondaryColor": "#F0F4FF",
    "tertiaryColor": "#E8EEFF",
    "edgeLabelBackground": "#FFFFFF",
    "clusterBkg": "#F8FAFF",
    "clusterBorder": "#C7D2E5",
    "background": "#FFFFFF",
    "fontFamily": "Inter, system-ui, sans-serif",
    "fontSize": 13
  },
  "preferredAspectRatio": "16:9",
  "flowchart": {
    "nodeSpacing": 50,
    "rankSpacing": 50
  }
}

How It Works