WXT

Appearance

ES Modules ​

Configure entrypoints to use ESM at runtime.

Currently, ESM entrypoints are opt-in, so you must configure each entrypoint with that in mind.

HTML Pages ≥0.0.1 ​

In general, you should always make HTML pages import ESM scripts, unless you need to support old browsers.

To make a script ESM, add type="module":

html
<script src="./main.ts"></script> 
<script src="./main.ts" type="module"></script>

Background ≥0.16.0 ​

In your background script, set type: "module":

ts
export default defineBackground({
  type: 'module', // !code ++
  main() {
    // ...
  },
});

WARNING

Only MV3 support ESM background scripts/service workers. When targeting MV2, the type option is ignored and the background is always bundled into a single file as IIFE.

Content Scripts ​

WXT does not include built-in support for ESM content scripts. There are several technical issues that make implementing a generic solution impossible. See Content Script ESM Support #357 for details.

Instead, depending on your requirements, you can implement ESM support manually. See the ESM Content Script UI example to get started.