Minify Transform · Unhead

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v3 (stable)

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Build Plugins

# Minify Transform

[Copy for LLMs](https://raw.githubusercontent.com/unjs/unhead/refs/heads/main/docs/head/1.guides/build-plugins/3.minify-transform.md)

Last updated Apr 9, 2026 by [Harlan Wilton](https://github.com/harlan-zw) in [refactor(bundler)!: named Unhead export, ctx-based transforms, dev-mode validate (#733)](https://github.com/unjs/unhead/pull/733).

On this page

- [What Does It Do?](#what-does-it-do)
- [Setup](#setup)
- [Available Minifier Backends](#available-minifier-backends)
- [Options](#options)
- [Runtime Minification](#runtime-minification)

**Quick Answer:** The minify transform runs at build time and minifies static string literals inside `useHead()` script and style tags. Uses heavier tools (rolldown/esbuild for JS, lightningcss for CSS) that never enter your SSR runtime bundle. Disabled by default, requires a minifier to be provided.

## [What Does It Do?](#what-does-it-do)

The transform finds `innerHTML` and `textContent` properties on `script` and `style` objects inside `useHead()` calls, then minifies them at build time:

Before (source)

After (build output)

```
useHead(unheadInstance, {
  script: [{
    innerHTML: \`
      // Analytics initialization
      window.dataLayer = window.dataLayer || [];
      function gtag() { dataLayer.push(arguments); }
      gtag('js', new Date());
    \`,
  }],
})
```

```
useHead(unheadInstance, {
  script: [{
    innerHTML: "window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments)}gtag(\"js\",new Date)",
  }],
})
```

The transform automatically skips `application/json`, `application/ld+json`, `speculationrules`, and `importmap` script types, and ignores strings shorter than 20 characters.

## [Setup](#setup)

The minify transform is disabled by default. Enable it by providing minifier functions:

```
import { Unhead } from '@unhead/vue/vite'
import { createJSMinifier } from '@unhead/bundler/minify/rolldown'
import { createCSSMinifier } from '@unhead/bundler/minify/lightningcss'

export default defineConfig({
  plugins: [
    Unhead({
      minify: {
        js: createJSMinifier(),
        css: createCSSMinifier(),
      },
    }),
  ],
})
```

## [Available Minifier Backends](#available-minifier-backends)

| Package | Function | Use case |
| --- | --- | --- |
| `@unhead/bundler/minify/rolldown` | `createJSMinifier()` | JS minification (Vite 8+) |
| `@unhead/bundler/minify/esbuild` | `createJSMinifier()` | JS minification (Vite 7) |
| `@unhead/bundler/minify/lightningcss` | `createCSSMinifier()` | CSS minification |

## [Options](#options)

```
Unhead({
  minify: {
    // Custom JS minifier, or false to disable
    js: createJSMinifier(),
    // Custom CSS minifier, or false to disable
    css: createCSSMinifier(),
    // Override the shared file filter
    filter: {
      include: [/my-special-file/],
      exclude: [/some-file/],
    },
  },
})
```

| Option | Type | Default | Description |
| --- | --- | --- | --- |
| `js` | `false \| MinifyFn` | — | JS minifier function, or `false` to disable |
| `css` | `false \| MinifyFn` | — | CSS minifier function, or `false` to disable |
| `filter` | `object` | inherited | Include/exclude file patterns (overrides the shared `filter`) |

### [Custom Minifiers](#custom-minifiers)

You can provide any async function that takes a string and returns the minified result (or `null` to skip):

```
Unhead({
  minify: {
    js: async (code) => {
      const result = await myMinifier(code)
      return result.code
    },
  },
})
```

## [Runtime Minification](#runtime-minification)

For runtime SSR minification (not build-time), see the [Minify Plugin](https://unhead.unjs.io/docs/head/guides/plugins/minify). The runtime plugin uses lightweight pure-JS minifiers suitable for edge and serverless environments.

[Edit this page](https://github.com/unjs/unhead/edit/main/docs/head/1.guides/build-plugins/3.minify-transform.md)

[Markdown For LLMs](https://raw.githubusercontent.com/unjs/unhead/refs/heads/main/docs/head/1.guides/build-plugins/3.minify-transform.md)

Did this page help you?

[useSeoMeta Transform Convert useSeoMeta() calls to useHead() at build time, saving ~3kb from your client bundle.](https://unhead.unjs.io/docs/head/guides/build-plugins/seo-meta-transform) [Devtools Inspect head tags, SEO metadata, entries, and source locations in the Vite DevTools panel. Enabled by default in development.](https://unhead.unjs.io/docs/head/guides/build-plugins/devtools)

On this page

- [What Does It Do?](#what-does-it-do)
- [Setup](#setup)
- [Available Minifier Backends](#available-minifier-backends)
- [Options](#options)
- [Runtime Minification](#runtime-minification)

[GitHub](https://github.com/unjs/unhead) [ Discord](https://discord.com/invite/275MBUBvgP)

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### Head Management

- [Getting Started](https://unhead.unjs.io/docs/typescript/head/guides/get-started/overview)
- [useHead](https://unhead.unjs.io/docs/typescript/head/api/composables/use-head)
- [useSeoMeta](https://unhead.unjs.io/docs/typescript/head/api/composables/use-seo-meta)
- [useHeadSafe](https://unhead.unjs.io/docs/typescript/head/api/composables/use-head-safe)
- [useScript](https://unhead.unjs.io/docs/typescript/head/api/composables/use-script)

### Schema.org

- [Getting Started](https://unhead.unjs.io/docs/typescript/schema-org/guides/get-started/overview)
- [useSchemaOrg](https://unhead.unjs.io/docs/typescript/schema-org/api/composables/use-schema-org)
- [Nodes](https://unhead.unjs.io/docs/typescript/schema-org/guides/core-concepts/nodes)
- [Recipes](https://unhead.unjs.io/docs/typescript/schema-org/guides/recipes/identity)

### Guides

- [Titles](https://unhead.unjs.io/docs/typescript/head/guides/core-concepts/titles)
- [Streaming SSR](https://unhead.unjs.io/docs/typescript/head/guides/core-concepts/streaming)
- [DOM Events](https://unhead.unjs.io/docs/typescript/head/guides/core-concepts/dom-event-handling)
- [Plugins](https://unhead.unjs.io/docs/typescript/head/guides/plugins/template-params)

### Tools

- [Meta Tag Generator](https://unhead.unjs.io/tools/meta-tag-generator)
- [OG Image Generator](https://unhead.unjs.io/tools/og-image-generator)
- [Schema.org Generator](https://unhead.unjs.io/tools/schema-generator)
- [Capo.js Analyzer](https://unhead.unjs.io/tools/capo-analyzer)

### Articles

- [What is Capo.js?](https://unhead.unjs.io/learn/guides/what-is-capo)

### Research

- [State of <head> in 2026](https://unhead.unjs.io/learn/research/state-of-head-2026)
- [Streaming Head Performance](https://unhead.unjs.io/learn/research/streaming-head-performance)
- [Capo.js Performance Research](https://unhead.unjs.io/learn/research/capo-performance-research)

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