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Is flatted ESM-only? Can you require() it?

A super light and fast circular JSON parser.

Last verified Sep 9, 2026 against flatted@3.4.4. JSON

ESM-only ESM-only since 3.0.0 — last CommonJS version is 2.0.2

flatted dropped its CommonJS build in 3.0.0 (May 2020). The last version you can require() on every Node.js version, including 18 and older, is 2.0.2, published Mar 29, 2020.

On Node.js 20.19+, 22.12+ and every newer release, require("flatted") works anyway: Node can load synchronous ES modules through require(). Verified on Node 20, 22, 24, 26. Node.js 18 and older still fail with ERR_REQUIRE_ESM.

Latest
3.4.4 (Jul 30, 2026)
Module format
ESM-only
Last CommonJS version
2.0.2
ESM-only since
3.0.0 (May 26, 2020)
TypeScript types
Bundled
Node engines
not declared
Weekly downloads
136.1M
License
ISC

Does flatted@3.4.4 actually load? Runtime test results

Installed and executed on Sep 9, 2026 with require("flatted") from a CommonJS file and import "flatted" from an ES module.

Runtimerequire("flatted")import "flatted"
Node.js 18✓ works✓ works
Node.js 20✓ works✓ works
Node.js 22✓ works✓ works
Node.js 24✓ works✓ works
Node.js 26✓ works✓ works
Bun 1.4✓ works✓ works

How to import flatted

ES modules (import)

import flatted from "flatted";

CommonJS (require)

// Node.js 20.19+ / 22.12+ / newer (package has no top-level await):
const flatted = require("flatted");

// Any Node.js version:
const flatted = await import("flatted");

// Or pin the last CommonJS release:
// npm install flatted@2.0.2

Module format by version

Derived from the type, main and exports fields of every stable release on npm (44 versions; the newest 44 shown).

VersionsFormatFirst published
3.0.0 – 3.4.4ESM-onlyMay 26, 2020
0.1.0 – 2.0.2CommonJSApr 26, 2018

Frequently asked

Is flatted ESM-only?

flatted@3.4.4 is ESM-only. flatted dropped its CommonJS build in 3.0.0 (May 2020). The last version you can require() on every Node.js version, including 18 and older, is 2.0.2, published Mar 29, 2020.

Which version of flatted still supports CommonJS / require()?

2.0.2 is the last version of flatted with a CommonJS build. Install it with "npm install flatted@2.0.2". Every version from 3.0.0 on is ESM-only.

How do I use flatted from a CommonJS file?

Use a dynamic import: const mod = await import("flatted"). On Node.js 20.19+, 22.12+ and newer, a plain require("flatted") also works for ESM packages that do not use top-level await. Alternatively pin flatted@2.0.2.

Does flatted work in Bun?

Yes. import "flatted" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does flatted ship TypeScript types?

Yes. flatted bundles its own type declarations; no @types package is needed.

Links

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