The CSSPageDescriptors interface represents a CSS declaration block for an @page at-rule.

The interface exposes style information and various style-related methods and properties for the page. Each multi-word property has versions in camel- and snake-case. This means, for example, that you can access the margin-top CSS property using the syntax style["margin-top"] or style.marginTop (where style is a CSSPageDescriptor).

A CSSPageDescriptors object is accessed through the style property of the CSSPageRule interface, which can in turn be found using the CSSStyleSheet API.

Instance properties

The following property names, in kebab-case (accessed using bracket notation) and camel-case (accessed using dot notation), each represent the value of a descriptor in the corresponding @page at-rule:

Instance methods

Examples

Inspecting a page at-rule

This example gets the CSSPageDescriptors for a @page at-rule, if the object is supported on the browser, and then logs its properties.

<pre id="log"></pre>

const logElement = document.querySelector("#log");
function log(text) {
  logElement.innerText = `${logElement.innerText}${text}\n`;
  logElement.scrollTop = logElement.scrollHeight;
}

#log {
  height: 280px;
  overflow: scroll;
  padding: 0.5rem;
  border: 1px solid black;
}

CSS

Below we define styles for the page using a @page at-rule. We assign different values for each margin property using the margin shorthand, and also specify the size. We don't set the page-orientation. This allows us to see how the properties map in the Web API object.

css

@page {
  margin: 1cm 2px 3px 4px;
  /* page-orientation: upright; */
  size: A4;
}

JavaScript

First we check if CSSPageDescriptors is defined on the global window object, and if not we log that the interface is not supported.

If CSSPageDescriptors is supported, we get the target stylesheet, and then gets the cssRules defined in that stylesheet. We need to get this stylesheet because the example is embedded in a separate frame with its own sheet (index 0 is the CSS for this page).

We then iterate through the rules defined for the live example and match any that are of type CSSPageRule, as these correspond to @page rules. For the matching objects we then log the style and all its values.

if (typeof window.CSSPageDescriptors === "undefined") {
  log("CSSPageDescriptors is not supported on this browser.");
} else {
  // Get stylesheets for example and then get its cssRules
  const myRules = document.getElementById("css-output").sheet.cssRules;
  for (const rule of myRules) {
    if (rule instanceof CSSPageRule) {
      log(`${rule.style}`);
      log(`margin: ${rule.style.margin}`);

      // Access properties using CamelCase syntax
      log(`marginTop: ${rule.style.marginTop}`);
      log(`marginRight: ${rule.style.marginRight}`);
      log(`marginBottom: ${rule.style.marginBottom}`);
      log(`marginLeft: ${rule.style.marginLeft}`);
      log(`pageOrientation: ${rule.style.pageOrientation}`);

      // Access properties using snake-case syntax
      log(`margin-top: ${rule.style["margin-top"]}`);
      log(`margin-right: ${rule.style["margin-right"]}`);
      log(`margin-left: ${rule.style["margin-left"]}`);
      log(`margin-bottom: ${rule.style["margin-bottom"]}`);
      log(`page-orientation: ${rule.style["page-orientation"]}`);

      log(`size: ${rule.style.size}`);

      // Log the original CSS text using inherited property: cssText
      log(`cssText: ${rule.style.cssText}`);
      log("\n");
    }
  }
}

Results

The results are shown below. Note that the style object displayed at the top of the log should be a CSSPageDescriptors to match the current specification, but may be a CSSStyleDeclaration in some browsers. Note also that the corresponding values for properties in camel- and snake-case match each other and the @page declaration, and that page-orientation is the empty string "" because it is not defined in @page.

CSSPageDescriptors