JavaScript modules in workersBaseline · Widely available

The Worker() constructor accepts { type: "module" } to load scripts that use import and export. Also known as ECMAScript modules or ESM in workers.

Supported in all major browsers for at least 30 months — safe to use without fallbacks. Baseline since Jun 6, 2023. Widely available since Dec 6, 2025.

How to use ↓Compare browsers

Browser support

DesktopChrome

1–79Not supported

80+Supportedsince Feb 4, 2020

Current: 155

Edge

12–79Not supported

80+Supportedsince Feb 7, 2020

Current: 154

Firefox

1–113Not supported

114+Supportedsince Jun 6, 2023

Current: 157

Safari

1–14.1Not supported

15+Supportedsince Sep 20, 2021

Current: 27

MobileChrome Android

18–79Not supported

80+Supportedsince Feb 4, 2020

Current: 155

Firefox Android

4–113Not supported

114+Supportedsince Jun 6, 2023

Current: 157

Safari iOS

1–14.5Not supported

15+Supportedsince Sep 20, 2021

Current: 27

How to use

This feature is Baseline widely available — use it freely, no fallback needed.

Example

Full syntax and examples are on MDN — see the links below.

Feature detection

JS · check before using

if ("Worker" in globalThis && "Worker" in Worker.prototype) {
  // Worker.Worker is available
}

Specification

html.spec.whatwg.org#dom-worker-dev ↗

Sub-features

Support for each part of the feature (4). The overall table above shows when the whole feature works.

Sub-feature	Chrome	Edge	Firefox	Safari	Chrome Android	Firefox Android	Safari iOS
Worker.Worker.ecmascript_modules	80	80	114	15	80	114	15
Worker.Worker.options_type_parameter	80	80	114	15	80	114	15
import.worker_support	80	80	114	15	80	114	15
import.worker_support	80	80	114	15	80	114	15