Draw.io Diagram Skill

Generate draw.io diagrams as native .drawio files. Optionally export to PNG, SVG, or PDF with the diagram XML embedded (so the exported file remains editable in draw.io), or generate a browser URL that opens the diagram directly in the draw.io editor.

How to create a diagram

1. Generate draw.io XML in mxGraphModel format for the requested diagram
2. Write the XML to a .drawio file in the current working directory using the Write tool
3. Handle the requested output format:
   • png / svg / pdf → locate the draw.io CLI (see draw.io CLI), export with --embed-diagram, then delete the source .drawio file. If the CLI is not found, keep the .drawio file and tell the user they can install the draw.io desktop app to enable export, or use url mode instead, or open the .drawio file directly
   • url → generate a browser URL from the XML and open it (see Browser URL output). Keep the .drawio file as a persistent local copy
   • (no format) → no extra step; the .drawio file is the output
4. Open the result — the exported file if exported, the browser URL if url, or the .drawio file otherwise. If the open command fails, print the file path (or URL) so the user can open it manually

Choosing the output format

Check the user's request for a format preference. Examples:

• /drawio create a flowchart → flowchart.drawio
• /drawio png flowchart for login → login-flow.drawio.png
• /drawio svg: ER diagram → er-diagram.drawio.svg
• /drawio pdf architecture overview → architecture-overview.drawio.pdf
• /drawio url flowchart for user login → opens browser at app.diagrams.net with the diagram, keeps login-flow.drawio locally

If no format is mentioned, just write the .drawio file and open it in draw.io. The user can always ask to export later.

Supported export formats

PNG, SVG, and PDF all support --embed-diagram — the exported file contains the full diagram XML, so opening it in draw.io recovers the editable diagram.

Browser URL output

When the user requests url format, generate a draw.io URL that opens the diagram directly in the browser editor at app.diagrams.net — no draw.io Desktop required.

How it works

1. The .drawio file is written to disk as usual (gives the user a persistent local copy they can re-edit)
2. The XML is compressed with Node.js's built-in zlib and base64-encoded
3. The result is embedded in a https://app.diagrams.net/#create=... URL
4. The URL is opened in the default browser

This uses only Node.js built-in modules (zlib, child_process) — no external dependencies.

URL generation

Run this node -e one-liner to read the .drawio file and print the URL (replace DIAGRAM.drawio with the actual filename):

URL=$(node -e '
const fs = require("fs");
const zlib = require("zlib");
const xml = fs.readFileSync(process.argv[1], "utf8");
const compressed = zlib.deflateRawSync(encodeURIComponent(xml)).toString("base64");
const payload = encodeURIComponent(JSON.stringify({ type: "xml", compressed: true, data: compressed }));
console.log("https://app.diagrams.net/?grid=0&pv=0&border=10&edit=_blank#create=" + payload);
' DIAGRAM.drawio)

The URL format matches the MCP Tool Server. Node.js's zlib.deflateRawSync and pako.deflateRaw both implement RFC 1951 and produce identical output, so URLs from either source are interchangeable.

Opening the URL

Why the .url workaround on Windows/WSL2? cmd.exe's start command treats & as a command separator and strips everything after # in URLs. The diagram payload lives in the #create=... fragment, so passing the URL directly causes it to be silently lost. A .url shortcut file preserves the URL intact.

macOS / Linux example:

open "$URL"      # macOS
xdg-open "$URL"  # Linux

WSL2 example:

TMPFILE=$(mktemp --suffix=.url)
printf '[InternetShortcut]\r\nURL=%s\r\n' "$URL" > "$TMPFILE"
cmd.exe /c start "" "$(wslpath -w "$TMPFILE")"

Windows (native) example:

echo [InternetShortcut] > %TEMP%\drawio.url
echo URL=%URL% >> %TEMP%\drawio.url
start "" "%TEMP%\drawio.url"

After opening

Print the URL so the user can copy or share it, and confirm the local file path:

Opened in browser: <URL>
Local file: DIAGRAM.drawio

The .drawio file stays on disk so the user can re-edit it later, attach it elsewhere, or export it to an image format on demand.

URL length

The URL embeds the full compressed diagram in its hash fragment. Very large diagrams may hit browser URL length limits (typically ~32K–2MB depending on the browser). For complex diagrams that exceed the limit, fall back to writing the .drawio file and opening it locally.

draw.io CLI

The draw.io desktop app includes a command-line interface for exporting.

Locating the CLI

First, detect the environment, then locate the CLI accordingly:

WSL2 (Windows Subsystem for Linux)

WSL2 is detected when /proc/version contains microsoft or WSL:

grep -qi microsoft /proc/version 2>/dev/null && echo "WSL2"

On WSL2, use the Windows draw.io Desktop executable via /mnt/c/...:

DRAWIO_CMD=`/mnt/c/Program Files/draw.io/draw.io.exe`

The backtick quoting is required to handle the space in Program Files in bash.

If draw.io is installed in a non-default location, check common alternatives:

# Default install path
`/mnt/c/Program Files/draw.io/draw.io.exe`

# Per-user install (if the above does not exist)
`/mnt/c/Users/$WIN_USER/AppData/Local/Programs/draw.io/draw.io.exe`

macOS

/Applications/draw.io.app/Contents/MacOS/draw.io

Linux (native)

drawio   # typically on PATH via snap/apt/flatpak

Windows (native, non-WSL2)

"C:\Program Files\draw.io\draw.io.exe"

Use which drawio (or where draw.io on Windows) to check if it's on PATH before falling back to the platform-specific path.

Export command

drawio -x -f <format> -e -b 10 -o <output> <input.drawio>

WSL2 example:

`/mnt/c/Program Files/draw.io/draw.io.exe` -x -f png -e -b 10 -o diagram.drawio.png diagram.drawio

Key flags:

• -x / --export: export mode
• -f / --format: output format (png, svg, pdf, jpg)
• -e / --embed-diagram: embed diagram XML in the output (PNG, SVG, PDF only)
• -o / --output: output file path
• -b / --border: border width around diagram (default: 0)
• -t / --transparent: transparent background (PNG only)
• -s / --scale: scale the diagram size
• --width / --height: fit into specified dimensions (preserves aspect ratio)
• -a / --all-pages: export all pages (PDF only)
• -p / --page-index: select a specific page (1-based)

Opening the result

WSL2 notes:

• wslpath -w <file> converts a WSL2 path (e.g. /home/user/diagram.drawio) to a Windows path (e.g. C:\Users\...). This is required because cmd.exe cannot resolve /mnt/c/... style paths.
• The empty string "" after start is required to prevent start from interpreting the filename as a window title.

WSL2 example:

cmd.exe /c start "" "$(wslpath -w diagram.drawio)"

File naming

• Use a descriptive filename based on the diagram content (e.g., login-flow, database-schema)
• Use lowercase with hyphens for multi-word names
• For export, use double extensions: name.drawio.png, name.drawio.svg, name.drawio.pdf — this signals the file contains embedded diagram XML
• After a successful export, delete the intermediate .drawio file — the exported file contains the full diagram
• For url mode, keep the .drawio file (no double extension) — the URL is a view/edit handle and the local file is the persistent copy

XML format

A .drawio file is native mxGraphModel XML. Always generate XML directly — Mermaid and CSV formats require server-side conversion and cannot be saved as native files.

Basic structure

Every diagram must have this structure:

<mxGraphModel adaptiveColors="auto">
  <root>
    <mxCell id="0"/>
    <mxCell id="1" parent="0"/>
    <!-- Diagram cells go here with parent="1" -->
  </root>
</mxGraphModel>

• Cell id="0" is the root layer
• Cell id="1" is the default parent layer
• All diagram elements use parent="1" unless using multiple layers

XML reference

For the complete draw.io XML reference including common styles, edge routing, containers, layers, tags, metadata, dark mode colors, and XML well-formedness rules, fetch and follow the instructions at: https://raw.githubusercontent.com/jgraph/drawio-mcp/main/shared/xml-reference.md

Troubleshooting

CRITICAL: XML well-formedness

• NEVER include ANY XML comments (<!-- -->) in the output. XML comments are strictly forbidden — they waste tokens, can cause parse errors, and serve no purpose in diagram XML.
• Escape special characters in attribute values: &, <, >, "
• Always use unique id values for each mxCell