6.3.3 • Public • Published

    CSS definitions of the web platform

    This package contains CSS property definitions scraped from the latest versions of web platform specifications in webref, with fixes applied to ensure (almost) all CSS value definitions can be parsed with CSSTree.


    The async listAll() method resolves with an object where the keys are spec shortnames, and the values are the data for that spec. Example:

    const css = require('@webref/css');
    const parsedFiles = await css.listAll();
    for (const [shortname, data] of Object.entries(parsedFiles)) {
      // do something with the json object

    CSS fragments that appear in the objects, in other words the contents of the properties[].value, properties[].newValues, atrules[].value, atrules[].descriptors[].value, selectors[].value and values[].value properties can be parsed with the CSSTree Value Definition Syntax parser. Example:

    const css = require('@webref/css');
    const { definitionSyntax } = require('css-tree');
    const parsedFiles = await css.listAll();
    for (const [shortname, data] of Object.entries(parsedFiles)) {
      for (const property of data.properties) {
        if (property.value) {
          try {
            const ast = definitionSyntax.parse(property.value);
            // do something with the ast
          catch {
            // one of the few value definitions that cannot yet be parsed by CSSTree


    The following guarantees are provided by this package:

    • All values in CSS files can be parsed by the version of CSSTree used in peerDependencies in package.json.
    • No duplicate definitions of CSS properties provided that CSS extracts of delta specs are not taken into account (such extracts end with -n.json, where n is a level number).
    • CSS extracts contain a base definition of all CSS properties that get extended by other CSS property definitions (those for which newValues is set).




    npm i @webref/css

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