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Is @csstools/css-parser-algorithms ESM-only? Can you require() it?

Algorithms to help you parse CSS from an array of tokens.

Last verified Sep 9, 2026 against @csstools/css-parser-algorithms@4.0.0. Markdown · JSON

ESM-only ESM-only since 4.0.0 — last CommonJS version is 3.0.5

@csstools/css-parser-algorithms dropped its CommonJS build in 4.0.0 (January 2026). The last version with a plain require()-able CommonJS entry is 3.0.5, published May 27, 2025; it declares support for Node.js >=18.

On Node.js 20.19+, 22.12+ and newer, require("@csstools/css-parser-algorithms") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Node.js 18 has no require(esm), and @csstools/css-parser-algorithms@4.0.0 declares Node.js >=20.19.0, so 18 is outside its supported range anyway.

@csstools/css-parser-algorithms@4.0.0 declares engines ">=20.19.0", so Node.js 18 is outside its supported range regardless of module format.

What to do

  1. On Node.js 20.19+, 22.12+ and newer, require("@csstools/css-parser-algorithms") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26.
  2. From a CommonJS file, use a dynamic import inside an async function: const cssParserAlgorithms = await import("@csstools/css-parser-algorithms"). That works on every Node.js version the package supports (>=20.19.0).
  3. If you need a synchronous require() or run Node.js 18: npm install @csstools/css-parser-algorithms@3.0.5, the last CommonJS release (published May 27, 2025); it declares Node.js >=18.
  4. @csstools/css-parser-algorithms@4.0.0 declares engines ">=20.19.0", so Node.js 18 is unsupported regardless: upgrade Node.js or pin an older release.
  5. TypeScript: types are bundled; install nothing extra.
Latest
4.0.0 (Jan 14, 2026)
Module format
ESM-only
Last CommonJS version
3.0.5
ESM-only since
4.0.0 (Jan 14, 2026)
TypeScript types
Bundled
Node engines
>=20.19.0
Weekly downloads
68.0M
License
MIT

Does @csstools/css-parser-algorithms@4.0.0 actually load? Runtime test results

Installed and executed on Sep 9, 2026 with require("@csstools/css-parser-algorithms") from a CommonJS file and import "@csstools/css-parser-algorithms" from an ES module.

Runtimerequire("@csstools/css-parser-algorithms")import "@csstools/css-parser-algorithms"
Node.js 18✗ failsERR_REQUIRE_ESM✓ works
Node.js 20✓ works✓ works
Node.js 22✓ works✓ works
Node.js 24✓ works✓ works
Node.js 26✓ works✓ works
Bun 1.4.0✓ works✓ works

How to import @csstools/css-parser-algorithms

ES modules (import)

import * as cssParserAlgorithms from "@csstools/css-parser-algorithms";

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS (require)

// Node.js 20.19+, 22.12+ and newer (verified):
const cssParserAlgorithms = require("@csstools/css-parser-algorithms");

// Any Node.js version the package supports (>=20.19.0), from an async function:
async function main() {
  const cssParserAlgorithms = await import("@csstools/css-parser-algorithms");
}

// Or pin the last CommonJS release (declares Node.js >=18):
// npm install @csstools/css-parser-algorithms@3.0.5

Module format by version

Derived from the type, main and exports fields of every stable release on npm, corrected where a runtime test of that version contradicted them (24 versions; the newest 24 shown).

VersionsFormatFirst published
4.0.0ESM-onlyJan 14, 2026
1.0.0 – 3.0.5Dual (CommonJS + ESM)Nov 14, 2022

Frequently asked

Is @csstools/css-parser-algorithms ESM-only?

@csstools/css-parser-algorithms@4.0.0 is ESM-only. @csstools/css-parser-algorithms dropped its CommonJS build in 4.0.0 (January 2026). The last version with a plain require()-able CommonJS entry is 3.0.5, published May 27, 2025; it declares support for Node.js >=18.

Which version of @csstools/css-parser-algorithms still supports CommonJS / require()?

3.0.5 is the last version of @csstools/css-parser-algorithms with a CommonJS build; it declares Node.js >=18. Install it with "npm install @csstools/css-parser-algorithms@3.0.5". Every version from 4.0.0 on is ESM-only.

How do I use @csstools/css-parser-algorithms from a CommonJS file?

From a CommonJS file, use a dynamic import inside an async function: const cssParserAlgorithms = await import("@csstools/css-parser-algorithms"). That works on every Node.js version the package supports (>=20.19.0). On Node.js 20.19+, 22.12+ and newer, require("@csstools/css-parser-algorithms") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin @csstools/css-parser-algorithms@3.0.5 (declares Node.js >=18).

Does @csstools/css-parser-algorithms work in Bun?

Yes. import "@csstools/css-parser-algorithms" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

Does @csstools/css-parser-algorithms ship TypeScript types?

Yes. @csstools/css-parser-algorithms bundles its own type declarations; no @types package is needed.

Links

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