[@rollup/plugin-swc] How to only minify, not transpile: vs rollup-plugin-swc-minify

[sidewayss]

The docs for @rollup/plugin-swc seem to be for TypeScript, and I'm using JavaScript and have no experience with TypeScript. This is my first experience with Node, Rollup, SWC, and packaging in general. I want to run the minification after I transpile with Babel, but Babel's minify makes that impossible because it processes the minification concurrently with the transpilation. I have tried using Terser and no joy there. The rollup-plugin-swc-minify works to my satisfaction in this regard, processing after Babel, but it doesn't allow clients to set minify options, instead it hard codes most all of them. I need to set some of those options.

Here is the example in the @rollup/plugin-swc readme:

import type { Options as SWCOptions } from '@swc/core';

declare type Options = {
  swc?: SWCOptions;
};

But I don't understand how to use that inside my rollup-config.mjs file. How do I specify the SWC options inside the call to swc() in the plugins property? There is no example of that. I have tried a couple of things but always end up with default settings: transpilation and no minification. And a question that probably belongs elsewhere: How do I tell SWC not to transpile and only to minify? I can see how rollup-plugin-swc-minify does it, but that's inside a Rollup plugin using SWC API, not a Rollup config file using Options.

I could fork or copy rollup-plugin-swc-minify to hard code my options, or publish a plugin that lets users specify all the options, but I'd much rather use a plugin that's part of Rollup itself and properly supported.

[potatohoney-p]

The TypeScript block describes the options object; you don't paste import type or declare type into your .mjs config. The SWC options go inside a swc property:

import swc from '@rollup/plugin-swc';

// In plugins, after your existing babel(...) plugin:
swc({
  swc: {
    swcrc: false,
    configFile: false,
    jsc: {
      parser: { syntax: 'ecmascript' },
      target: 'esnext',
      minify: {
        compress: { drop_console: true }, // example; choose your own options
        mangle: false,
      },
    },
    minify: true,
  },
})

This enables minification and avoids targeting an older language level in SWC. swcrc: false / configFile: false keep a separate SWC config from affecting this example. Don't enable drop_console unless you actually want to remove those calls.

There is an important distinction, though: the official plugin calls @swc/core.transform() in Rollup's per-module transform hook. Putting it after Babel makes that transform see Babel's output, but target: 'esnext' does not turn it into the standalone minify-only API or a final-bundle minifier.

If your requirement is specifically “call SWC's minifier on the finished chunks, without another SWC transpilation pass,” you can put a small plugin object directly in the same .mjs file—no fork or published package needed. For ES-module output:

import { minify } from '@swc/core';

const swcMinifyOnly = {
  name: 'swc-minify-only',
  async renderChunk(code) {
    const result = await minify(code, {
      module: true, // this example is for output.format: 'es'
      compress: { drop_console: true },
      mangle: false,
      sourceMap: true,
    });
    return { code: result.code, map: result.map ?? null };
  },
};

// plugins: [your existing babel(...) plugin, swcMinifyOnly]
// output: { ..., format: 'es', sourcemap: true }

Use this instead of the swc(...) minification step above. renderChunk runs during output generation, after the input-module transforms. This is a custom wrapper around SWC's API, not a minify-only mode exposed by @rollup/plugin-swc.

I checked both approaches with Rollup 4.66.0, @rollup/plugin-swc 0.4.1, @swc/core 1.16.20, @rollup/plugin-babel 7.1.0 and Babel/core + preset-env 7.29.7 on Node 24.22.1. In a small ES-output fixture, Babel lowered optional chaining before SWC ran, the configured console removal took effect, the exported function retained its tested results, and the final source map retained the original source content. That verifies this pipeline, not your unspecified Babel setup or all possible minifier settings.