Free online MMD to PNG converter

What the MMD format is

In the mind-map and flowchart context, .mmd is a plain-text Mermaid diagram file. It contains Mermaid syntax describing nodes, connections, labels, directions, and diagram types such as flowcharts, mind maps, sequence diagrams, and class diagrams.

Mermaid editors, documentation systems, code repositories, and diagramming workflows create or use MMD files. A typical file contains source such as flowchart TD; A[Start] --> B[Finish], rather than pre-rendered pixels. The file can be edited with any text editor, but it requires a Mermaid-compatible renderer to produce an image.

What the PNG format is

PNG is a raster image format supported by web browsers, office applications, image editors, presentation software, and most operating systems. It suits diagrams because it uses lossless compression, keeps sharp solid-color edges, and supports transparency.

Use PNG when the destination accepts images but does not render Mermaid syntax, or when you need a fixed visual snapshot for documentation, email, presentations, or archiving. PNG is not ideal for unlimited scaling; SVG is usually better when the diagram must remain vector-sharp at any size.

How to convert MMD to PNG

Using the built-in online converter

You can convert the file on 101convert.com for free without installing software. Upload the .mmd file, select PNG as the output format if prompted, start the conversion, and download the rendered image. The source must contain valid Mermaid syntax; a file with unrelated text or unsupported syntax may fail to render.

Using Mermaid CLI

Mermaid CLI is the most direct desktop or command-line method:

1. Install Node.js, then install Mermaid CLI with npm install -g @mermaid-js/mermaid-cli.
2. Save the Mermaid source as a file such as diagram.mmd.
3. Render it with mmdc -i diagram.mmd -o diagram.png.

The command reads the Mermaid source, renders it through a browser engine, and writes the PNG output. Useful options include -b transparent for a transparent background, -s 2 for a two-times scale factor, -w 2000 for a target width, and -H 1200 for a target height. For example:

mmdc -i diagram.mmd -o diagram.png -b transparent -s 2

On systems where Chromium dependencies are unavailable, Mermaid CLI may require the operating system packages used by its Puppeteer browser engine. A rendering configuration can be supplied with -p puppeteer-config.json.

Quality and compatibility limitations

PNG output contains only the rendered appearance; node positions, links, labels, and Mermaid syntax cannot be edited as diagram objects. Keep the original .mmd file with the PNG when future edits are likely.

Rendering can differ between Mermaid versions because diagram syntax, default themes, fonts, and layout algorithms change. Install a compatible Mermaid CLI version and verify custom fonts on the rendering machine. Increase -s, -w, or -H when small labels look blurred, but avoid enlarging a low-resolution PNG after conversion.