Mermaid.ink API

Base URL

https://mermaid.ink

Authentication

No key. The hosted instance is a courtesy; the project is open source and containerised for self-hosting.

Rate limit

Not published. Cache rendered images rather than re-rendering the same diagram on every page view.

Pricing

Free and open source, self-hostable.

CORS

Enabled — callable directly from browser JavaScript

Official docs

Read the docs

Every request below was executed against the live API on 2026-08-21, and the response shown is the real body it returned — not an illustration.

curl 'https://mermaid.ink/img/Z3JhcGggVEQ7CiAgQVtDbGllbnRdLS0-QltBUEldOwogIEItLT5DWyhEYXRhYmFzZSldOw==?type=png'

const res = await fetch("https://mermaid.ink/img/Z3JhcGggVEQ7CiAgQVtDbGllbnRdLS0-QltBUEldOwogIEItLT5DWyhEYXRhYmFzZSldOw==?type=png");
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);

import requests

res = requests.get("https://mermaid.ink/img/Z3JhcGggVEQ7CiAgQVtDbGllbnRdLS0-QltBUEldOwogIEItLT5DWyhEYXRhYmFzZSldOw==?type=png", timeout=20)
res.raise_for_status()
print(res.json())

# This endpoint returns image/png, not JSON.
# The response body is the image itself, so it can be used directly as an
# <img src="..."> or saved to a file — there is nothing to parse.
#
# Verified: HTTP 200, Content-Type: image/png

(body)image/png

The rendered diagram. There is no JSON envelope; the response body is the image itself, usable directly in an `<img src>`.

(default content type)image/jpeg

Without `?type=png` the `/img/` path returns JPEG, whose compression blurs thin diagram lines and small text.

(svg path)image/svg+xml

The `/svg/` path returns text-based SVG, which scales cleanly and can be styled or embedded inline.

(400 responses)n/a

A syntax error in the diagram, or invalid base64, returns an error rather than an image. Test the source in the Mermaid live editor first.

• Embed architecture diagrams in a README on a forge that does not render Mermaid
• Include flowcharts in HTML email or a PDF report
• Generate sequence diagrams from code comments during a docs build
• Post a diagram into Slack or Discord as an image
• Render diagrams in a static site generator without adding a JavaScript dependency