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Agent-friendly API

QuickChart exposes machine-readable API metadata and validation endpoints for agents, automations, and other clients that need structured responses.

Discovery files​

Use the OpenAPI file for parameters, response content types, limits, and auth details. A YAML copy is also available.

The reference covers charts, QR generation and reading, barcodes, word clouds, GraphViz, table images, watermarking, and Google Image Charts compatibility. The /qr-url and /qr-urls endpoints return URLs when you do not need image bytes immediately.

Validate a chart config​

Use POST /api/validate-chart to check a chart request before rendering or retrying. The payload is the same shape as POST /chart, but the response is JSON.

curl -X POST https://quickchart.io/api/validate-chart \
  -H 'Content-Type: application/json' \
  -d '{
    "version": "4",
    "width": 700,
    "height": 360,
    "format": "png",
    "chart": {
      "type": "bar",
      "data": {
        "labels": ["Jan", "Feb", "Mar"],
        "datasets": [{ "label": "Revenue", "data": [120, 150, 180] }]
      }
    }
  }'

Validation renders the configuration and discards the image. It is subject to the same request limits as rendering. A successful response includes normalized request parameters and a render check (the byte count below is illustrative):

{
  "success": true,
  "errors": [],
  "warnings": [],
  "normalized": {
    "width": 700,
    "height": 360,
    "devicePixelRatio": 2,
    "backgroundColor": "transparent",
    "version": "4",
    "format": "png",
    "encoding": "url",
    "chartType": "bar",
    "chartIsString": false,
    "authenticated": false
  },
  "renderCheck": {
    "contentType": "image/png",
    "bytes": 12345
  }
}

Invalid configurations return HTTP 400 with one or more error strings. Invalid signatures return HTTP 403, and rate-limited requests return HTTP 429. For example:

{
  "success": false,
  "errors": ["Chart error: Invalid input"],
  "warnings": [],
  "normalized": {
    "width": 500,
    "height": 300,
    "format": "png"
  }
}

Check warnings even when success is true. For example, the validator warns when it detects v3 or v4 options in a request using the default Chart.js v2. It also warns when a chart uses external data that should only be cached briefly.

Validation does not return or save an image. Send the same body to /chart to get the output. For JPEG, WebP, and PDF, check the actual render response too: chart validation checks the underlying chart render, but does not perform the final file conversion.

Validate a QR code config​

Use POST /api/validate-qr to check a QR request before rendering. The payload is the same shape as POST /qr.

curl -X POST https://quickchart.io/api/validate-qr \
  -H 'Content-Type: application/json' \
  -d '{
    "text": "https://example.com",
    "format": "png",
    "size": 300,
    "margin": 4
  }'

On success, render the same body with POST /qr. QR validation rejects unsupported formats, even though the rendering endpoint falls back to PNG for unrecognized format names.

Generate a chart config from text​

Use POST /natural/config when you want a natural-language chart draft but need editable JSON instead of only an image.

curl -X POST https://quickchart.io/natural/config \
  -H 'Content-Type: application/json' \
  -d '{
    "description": "bar chart showing revenue Jan-Mar with values 120, 150, 180",
    "width": 700,
    "height": 360,
    "backgroundColor": "white"
  }'

The response includes:

  • chart: generated Chart.js config as a string
  • chartUrl: saved chart image URL
  • chartMakerUrl: editor URL
  • warnings: notes to show before production use

Validate generated configs with /api/validate-chart before embedding them in production workflows.