Diagram Renderer: Mermaid & Graphviz to SVG, PNG, PDF

Turn Mermaid or Graphviz (DOT) code into clean SVG, PNG or PDF files, each with a link you can share. Send one diagram or a batch of up to 100. Diagrams that fail to render are not charged, and the parser's error message comes back so you (or your AI agent) can fix the code and retry.

Made for:

• AI agents and MCP clients. LLMs write Mermaid well but can't display it. This Actor gives them an image URL.
• Docs and reporting pipelines that keep diagrams as code.
• n8n, Make, Zapier and Apify integrations that need a picture of a workflow, an architecture, or a data flow.

What it does

1. You send diagram code, for example a Mermaid flowchart, a sequenceDiagram, or a Graphviz digraph { ... }.
2. The Actor renders it in a locked-down renderer with no network access.
3. Each file is saved to the run's key-value store. You get one dataset row per diagram containing the file url, format, width, height, bytes, and an errorCode and error if it failed.

Supported diagram types

• Mermaid: flowchart/graph, sequence, class, state, entity-relationship, Gantt, pie, mindmap, timeline, user journey, Git graph, quadrant, XY chart, Sankey, block, packet, requirement, C4, architecture, kanban, radar, treemap, and the other diagram types Mermaid supports.
• Graphviz: the DOT language, with the dot, neato, fdp, sfdp, circo, twopi, osage and patchwork layout engines.

Engine auto-detection: code that starts with digraph { or graph { (including strict and named graphs) is treated as Graphviz. Everything else is treated as Mermaid. You can also set engine explicitly.

Input

One diagram

{
  "source": "flowchart LR\n  A[Request] --> B{Cached?}\n  B -->|yes| C[Return]\n  B -->|no| D[Fetch] --> C",
  "format": "png"
}

A batch of diagrams

Top-level options act as defaults for every item, and each item can override them.

{
  "format": "svg",
  "theme": "neutral",
  "diagrams": [
    { "id": "login-flow", "source": "sequenceDiagram\n  User->>App: Log in\n  App->>API: POST /session\n  API-->>App: 200 OK" },
    { "id": "deps", "source": "digraph { rankdir=LR; app -> api -> db; app -> cache }", "format": "png", "scale": 3 },
    { "id": "schema", "source": "erDiagram\n  CUSTOMER ||--o{ ORDER : places", "format": "pdf" }
  ]
}

Field	Type	Default	Notes
source	string	example flowchart	Code for one diagram. Ignored when diagrams is set. Max 50,000 characters.
diagrams	array	—	Up to 100 items. Each item is an object or a plain string (treated as its source).
id (item)	string	position (1, 2, …)	Used in the file name: diagram-<id>.<format>.
engine	auto · mermaid · graphviz	auto
format	png · svg · pdf	png	PDF is one page, sized to the diagram.
theme	default · neutral · dark · forest · base	default	Mermaid only.
background	CSS color	white (dark grey for the dark theme)	e.g. transparent, #f5f5f5, rgb(0,0,0).
scale	0.5–4	2	PNG pixel density. 2 gives sharp, retina-quality images.
width	16–8000 px	natural size	The height follows the aspect ratio.
layout	dot · neato · fdp · sfdp · circo · twopi · osage · patchwork	dot	Graphviz only.

Output

One dataset item per diagram:

{
  "id": "login-flow",
  "index": 0,
  "ok": true,
  "engine": "mermaid",
  "format": "svg",
  "url": "https://api.apify.com/v2/key-value-stores/<storeId>/records/diagram-login-flow.svg",
  "key": "diagram-login-flow.svg",
  "contentType": "image/svg+xml",
  "bytes": 24117,
  "width": 450,
  "height": 297,
  "renderMs": 182,
  "charged": true,
  "errorCode": null,
  "error": null,
  "warnings": []
}

A failed diagram looks like this. It is not charged, and the rest of the batch keeps going:

{
  "id": "bad-one",
  "ok": false,
  "url": null,
  "errorCode": "SYNTAX_ERROR",
  "error": "Mermaid: Parse error on line 2:\n...A --> (((\n-------^\nExpecting 'SQS', 'DOUBLECIRCLESTART', ... got 'PS'",
  "charged": false
}

Error codes: SYNTAX_ERROR (fix the diagram code), INVALID_INPUT (a bad option value, or a remote image), LIMIT_EXCEEDED (input or output too large), TIMEOUT, RENDER_FAILED, STORAGE_FAILED.

The files are in the run's key-value store (Storage → Key-value store → Diagrams). A RUN_SUMMARY record holds the counts, charges and timings for the run.

Use it from the API

Call the synchronous endpoint to get the dataset rows (with file URLs) in a single request:

curl -X POST "https://api.apify.com/v2/acts/DryBoneslabs~diagram-renderer/run-sync-get-dataset-items?token=<YOUR_TOKEN>" \
  -H "Content-Type: application/json" \
  -d '{"source": "graph TD; A-->B; B-->C", "format": "png"}'

AI agents can also find and call the Actor through the Apify MCP server.

Pricing

Pay per event. You only pay for diagrams that render successfully.

Event	Price
Diagram rendered (one SVG, PNG or PDF file)	$0.008 ($8 per 1,000)
Actor start	$0.00005 per run per GB of memory (one event at the default 1 GB; Apify's standard start fee)

• Failed diagrams (syntax errors, invalid options, timeouts) are not charged.
• No platform usage fees on top: compute is included in the price.
• Max cost per run is respected. When your limit is reached, the Actor stops cleanly after the last paid diagram, and the remaining items are listed as skipped in the run summary.

Example: a batch of 50 PNG diagrams costs 50 × $0.008 = $0.40 (plus $0.00005 for the start).

Limits

Limit	Value
Diagrams per run	100
Source size	50,000 characters per diagram
PNG size	16 megapixels, 8,000 px per side. Larger diagrams are scaled down automatically, with a warning.
Diagram size (PNG/PDF)	16,000 px per side before scaling
File size	20 MB
Time per diagram	20 s. After 3 timeouts in a run, the remaining items are skipped (not charged).

Security and privacy

• No network access while rendering. Diagram code cannot fetch URLs, call internal services or load remote images, fonts or stylesheets. Every request from the renderer is blocked.
• Mermaid runs with securityLevel: "strict": HTML in labels is sanitized and click callbacks are disabled. %%{init}%% directives cannot change security settings.
• Links are stripped from output files. External links, images, scripts and @import rules are removed from SVG output, so the files are safe to embed. If a file had any removed, the item's warnings say so.
• Graphviz runs as WebAssembly with no access to the file system.
• Your diagram code is not logged or stored anywhere except your own run's storage.

FAQ

My Mermaid diagram fails with a syntax error, but it works on the Mermaid website. This Actor uses Mermaid 12. Check the error text: it shows the line and the token the parser expected. Newer syntax may need a newer Mermaid version than the one you used elsewhere.

Can I use images or icons from URLs inside diagrams? No. The renderer has no internet access, for security. Embed small images as data:image/png;base64,... URIs instead.

Why does my SVG look different in Inkscape, Word or PowerPoint? Mermaid flowchart labels use HTML (foreignObject), which browsers display perfectly but some desktop apps don't. Use PNG or PDF for Office documents.

Do theme and background apply to Graphviz? background does. theme is Mermaid-only, so style Graphviz with DOT attributes (node [style=filled, fillcolor="#e8f0fe"]).

How long do files stay available? As long as the run's storage is retained under your Apify plan's data retention. Download or copy files you want to keep.

Is this an official Mermaid or Graphviz product? No. This Actor is an independent tool. It is not affiliated with or endorsed by the Mermaid or Graphviz projects. It uses the open-source Mermaid (MIT) and Graphviz (EPL, via the Apache-2.0 @hpcc-js/wasm-graphviz build) libraries.

Changelog

• 1.0: First release. Mermaid and Graphviz input; SVG, PNG and PDF output; batches of up to 100 diagrams; pay-per-event pricing.