Minify

minify is a simple boolean toggle that turns minification on or off. When enabled, the active transformer (esbuild, swc, or oxc — whichever you configured via the transformer option) minifies the emitted output. Packem does not ship a separate minifier or a minifier-selection mechanism: the minifier is the transformer.

minify?: boolean

There is no string form ('esbuild', 'swc', …), no object form, and no function form. minify is either true or false.

Default behavior

minify defaults to true when NODE_ENV === 'production', and false otherwise. You usually don't need to set it at all — building in production mode enables minification automatically.

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  // minify is implicitly true when NODE_ENV === 'production'
})

Enabling minification explicitly

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  minify: true,
})

Conditional minification

Drive the toggle from the environment when you want a single config to behave differently across builds:

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  minify: process.env.NODE_ENV === 'production',
})

The minifier is your transformer

Because minification is performed by the active transformer, switching the transformer also switches which engine minifies your output. To minify with esbuild:

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  minify: true,
})

To minify with swc instead, just import a different transformer:

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/swc'

export default defineConfig({
  transformer,
  minify: true,
})

The minify: true flag is unchanged — only the imported transformer decides which engine does the work.

Preserving function & class names (keepNames)

When using the esbuild transformer, esbuild can preserve original function/class names through minification (so fn.name and stack traces stay readable). Packem leaves this off by default — matching esbuild's own default — and lets you opt in via the transformer's rollup config. keepNames nests under rollup.esbuild:

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  minify: true,
  rollup: {
    esbuild: {
      keepNames: true, // opt in when you rely on runtime name reflection
    },
  },
})

HTML / CSS template-literal minification

Minification of HTML and CSS embedded in tagged template literals is a separate, opt-in feature configured under rollup.minifyHTMLLiterals — not via minify:

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  rollup: {
    minifyHTMLLiterals: {},
  },
})

See the Minify HTML literals example for details.

CSS minification

CSS minification is not controlled by minify. It is configured through the css option's minifier. See the CSS guide for the full configuration.

Related Options

• Target - Compilation targets
• Source Maps - Debug information
• Tree Shaking - Dead code elimination
• Analyze - Bundle size analysis
• CSS - CSS handling and minification
• Optimization - Build optimization guide