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The prefer_css_page_size parameter allows you to control whether CSS-defined page sizes take precedence over the API-specified paper size.

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Overview

When rendering a webpage to PDF, there can be a conflict between the page size specified in the API request (via the size parameter) and any page size defined in the document’s CSS using @page rules. The prefer_css_page_size parameter determines which of these takes precedence.

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Parameter details

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prefer_css_page_size
boolean
default:false
Controls whether CSS-defined page sizes take precedence over the API-specified paper size

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Usage

{
  "parts": "https://example.com",
  "size": {
    "preset": "a4"
  },
  "prefer_css_page_size": true
}

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Behavior

  • true: CSS page size defined in @page rules takes precedence over the size parameter. Content will be rendered using the dimensions specified in CSS.
  • false: The size parameter takes precedence over any CSS-defined page size. Content will be scaled to fit the specified paper size.

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Use cases

This parameter is particularly useful for:
  1. CSS-driven layouts: When your HTML content includes specific @page size rules that are essential to the layout design.
  2. Consistent sizing across sources: When you want to ensure all documents use the same paper size regardless of their CSS settings.
  3. Web-to-print workflows: When converting web content that already has print-specific CSS rules that should be respected.

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Example with CSS @page rules

Consider HTML content with the following CSS: 
@page {
  size: 5in 8in; /* Sets page size to 5 inches by 8 inches */
}

.content {
  margin: 0.5in;
}

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With prefer_css_page_size true

{
  "parts": "<html><style>@page { size: 5in 8in; }</style><body>Content</body></html>",
  "size": {
    "preset": "a4"
  },
  "prefer_css_page_size": true
}
Result: The PDF will use the 5in × 8in size from the CSS, ignoring the A4 size specified in the API request.

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With prefer_css_page_size false

{
  "parts": "<html><style>@page { size: 5in 8in; }</style><body>Content</body></html>",
  "size": {
    "preset": "a4"
  },
  "prefer_css_page_size": false
}
Result: The PDF will use the A4 size (210mm × 297mm) specified in the API request, and the content will be scaled to fit.