Pikacss use

Use PikaCSS

PikaCSS is an instant on-demand atomic CSS-in-JS engine. It transforms statically analyzable pika() calls into class-name literals at build time, emits the matching atomic CSS, and generates TypeScript declarations for the compile-time globals.

• Docs: https://pikacss.github.io/getting-started/
• API Reference: https://pikacss.github.io/api/
• Source: https://github.com/pikacss/pikacss

Reference Files

Load the smallest relevant reference instead of guessing from memory:

File	When to read
references/build-options.md	Build plugin options, scan patterns, codegen paths, custom function names, bundler roots, or HMR
references/customizations.md	Variables, theming, keyframes, preflights, selectors, shortcuts, __shortcut, __layer, __important, CSS value fallbacks, or typed config fragments
references/plugin-reset.md	Choosing and configuring a reset style
references/plugin-icons.md	Icon shortcuts, Iconify collections, Node versus neutral adapters, processor metadata, or icon troubleshooting
references/plugin-fonts.md	Google Fonts, @font-face, @import, font families, or providers
references/plugin-typography.md	Prose shortcuts and --pk-prose-* variables
references/plugin-design-tokens.md	Inline or file-backed design tokens, W3C token JSON, design.md, themes, aliases, pruning, or runtime adapters
references/plugin-development.md	Creating plugins, lifecycle hooks, diagnostics, engine APIs, config augmentation, external file dependencies, or testing

Non-Negotiable Facts

• Node-targeted PikaCSS packages declare engines.node as >=22. The platform-neutral packages (@pikacss/core, @pikacss/plugin-icons, @pikacss/plugin-design-tokens) declare none on purpose.
• The Vite adapter supports Vite 7 and 8 (^7.0.0 || ^8.0.0).
• pika is a generated compile-time global. Never import it.
• Arguments must be statically analyzable. Runtime values belong in CSS variables, variant maps, or predefined shortcuts.
• The built-in AST processors support the JS family (js, mjs, cjs, jsx, ts, mts, cts, tsx) and Vue SFCs. Do not claim Svelte, Astro, or plain HTML source transforms are supported.
• Config discovery is project-root-only. Generated declaration files must be included in the TypeScript program.

How the Compile-Time Macro Works

const className = pika({ display: 'flex', color: 'red' })

is transformed into a plain literal such as:

const className = 'pk-a1b2 pk-c3d4'

The generated CSS contains the corresponding atomic rules. No PikaCSS runtime is shipped to the browser.

Installation

Vite and other unplugin integrations

pnpm add -D @pikacss/core @pikacss/unplugin-pikacss

Nuxt

pnpm add -D @pikacss/core @pikacss/nuxt-pikacss

Optional packages

pnpm add -D @pikacss/plugin-reset
pnpm add -D @pikacss/plugin-icons
pnpm add -D @pikacss/plugin-fonts
pnpm add -D @pikacss/plugin-typography
pnpm add -D @pikacss/plugin-design-tokens
pnpm add -D @pikacss/eslint-config

Install @pikacss/core directly because application config files and official plugins consume its public types and helpers.

Build Plugin Setup

Vite

// vite.config.ts
import pikacss from '@pikacss/unplugin-pikacss/vite'
import { defineConfig } from 'vite'

export default defineConfig({
  plugins: [pikacss()],
})

The Vite adapter uses enforce: 'pre', so [vue(), pikacss()] is supported even though listing PikaCSS first remains clearer.

Other bundlers

Bundler	Import path
Vite	@pikacss/unplugin-pikacss/vite
Rollup	@pikacss/unplugin-pikacss/rollup
Webpack	@pikacss/unplugin-pikacss/webpack
esbuild	@pikacss/unplugin-pikacss/esbuild
Rspack	@pikacss/unplugin-pikacss/rspack
Rolldown	@pikacss/unplugin-pikacss/rolldown

Each subpath exports a plugin factory. Add pikacss() to the target bundler's plugin array. Read references/build-options.md before recommending non-default options.

Nuxt

// nuxt.config.ts
export default defineNuxtConfig({
  modules: ['@pikacss/nuxt-pikacss'],
})

Do not also add @pikacss/unplugin-pikacss/vite. The Nuxt module owns the Vite wiring and imports pika.css through a generated Nuxt plugin/template.

Generated Files and CSS Import

The build integration writes:

• Runtime CSS as internal state under .pikacss/ in the project root. Each dev/build run owns its own file; the location is not configurable.
• pika.gen.ts by default. TypeScript codegen may be redirected or disabled.
• pika.config.js only when autoCreateConfig: true; the default is false.

For non-Nuxt applications, import the virtual CSS module in the entry file:

import 'pika.css'

The virtual module resolves to the current run's internal runtime CSS automatically.

TypeScript inclusion

A root-level pika.gen.ts is not included by scaffolded projects whose tsconfig only includes src. Prefer either:

// vite.config.ts
pikacss({ tsCodegen: './src/pika.gen.ts' })

or:

{
  "include": ["src", "pika.gen.ts"]
}

A standalone tsc --noEmit run also needs the generated file to exist. Run a build/codegen step first or commit pika.gen.ts when CI typechecks before building.

Engine Configuration

Supported root config names, in discovery priority order:

• pika.config.{ts,mts,cts,js,mjs,cjs}
• pikacss.config.{ts,mts,cts,js,mjs,cjs}

Use at most one config file. A config file is optional when the default engine behavior is sufficient.

// pika.config.ts
import { defineEngineConfig } from '@pikacss/core'
import { icons } from '@pikacss/plugin-icons/node'
import { reset } from '@pikacss/plugin-reset'

export default defineEngineConfig({
  prefix: 'pk-',
  plugins: [reset(), icons()],
})

The Node icons adapter is the normal choice in bundler config when locally installed @iconify-json/* packages or autoInstall are required. The neutral @pikacss/plugin-icons entry only handles custom collections and CDN loading unless custom runtime capabilities are supplied.

Core config options

Option	Type	Default	Purpose
plugins	EnginePlugin[]	[]	Engine plugins
prefix	string	'pk-'	Atomic class prefix
defaultSelector	string	'.%'	Atomic selector template; % is the generated class placeholder
preflights	Preflight[]	[]	Global CSS emitted before utilities
cssImports	string[]	[]	CSS @import statements prepended to output
layers	Record<string, number>	{ preflights: 1, utilities: 10 }	CSS layer ordering
defaultPreflightsLayer	string	'preflights'	Default preflight layer
defaultUtilitiesLayer	string	'utilities'	Default atomic utility layer
autocomplete	AutocompleteConfig	{}	Generated IDE/type autocomplete configuration

Plugin-augmented config keys

Core internal plugins add important, selectors, shortcuts, variables, and keyframes. Official packages additionally augment keys such as reset, icons, fonts, and designTokens when their modules are imported.

Read references/customizations.md for exact shapes. Do not invent removed define* wrapper helpers for reusable config fragments.

Usage

Style items

pika() accepts one or more style items:

• A style definition object.
• A registered shortcut name.
• An unresolved string, which is preserved as an existing/raw class name.

const classes = pika(
  'existing-class',
  'flex-center',
  {
    display: 'flex',
    alignItems: 'center',
    fontSize: '1rem',
  },
)

Both camelCase and kebab-case CSS properties are accepted.

CSS value fallbacks

Use [primaryValue, fallbackValues[]]. Fallback declarations are emitted first, then the primary value:

pika({
  color: ['oklch(0.7 0.15 220)', ['rgb(0 120 255)', 'blue']],
})

Do not use a flat array such as ['red', 'blue']; that is not the fallback tuple shape.

Function variants

Syntax	Output	Purpose
pika(...)	Configured default	Uses transformedFormat
pika.str(...)	string	Forces a space-separated class string
pika.arr(...)	string[]	Forces an array of class names

Nested selectors

Built-in pseudo selectors use a $ prefix; CSS at-rules are written directly. Named aliases must be registered under selectors.definitions.

pika({
  color: 'red',
  '$:hover': { opacity: '0.8' },
  '$::before': { content: '""' },
  '@media (min-width: 768px)': { fontSize: '1.2rem' },
  '@dark': { color: 'white' }, // custom alias; register it first
})

selectors: {
  definitions: [
    ['@dark', 'html.dark $'],
  ],
}

Inside a selector definition, $ is replaced by the generated atomic class selector.

Per-definition controls

pika({
  __shortcut: ['flex-center', 'card'],
  __layer: 'components',
  __important: true,
  gap: '1rem',
})

• __shortcut expands shortcuts before the object's own declarations, so explicit declarations win.
• __layer selects a configured layer.
• __important applies !important, including to expanded shortcut declarations.

Official Plugins

Plugin	Package	Important adapter rule	Reference
Reset	@pikacss/plugin-reset	No runtime split	references/plugin-reset.md
Icons	@pikacss/plugin-icons	Use /node for local Iconify packages and autoInstall; neutral entry supports custom/CDN sources	references/plugin-icons.md
Fonts	@pikacss/plugin-fonts	No runtime split	references/plugin-fonts.md
Typography	@pikacss/plugin-typography	No runtime split	references/plugin-typography.md
Design Tokens	@pikacss/plugin-design-tokens	Use /node for JSON/Markdown file paths; neutral entry supports inline tokens	references/plugin-design-tokens.md

Each plugin factory belongs in plugins. Its module import also activates the corresponding EngineConfig augmentation.

Public Define Helpers

@pikacss/core exposes two public define helpers:

• defineEngineConfig(config)
• defineEnginePlugin(plugin)

For reusable styles, preflights, selectors, shortcuts, variables, or keyframes, use plain object literals with satisfies or explicit type annotations.

ESLint

// eslint.config.mjs
import pikacss from '@pikacss/eslint-config'

export default [pikacss()]

The default export returns a flat-config entry. Keep its fnName aligned with the build plugin when using a custom compile-time function name.

Troubleshooting

Symptom	Likely cause	Fix
Config not detected	Wrong name, duplicate configs, or wrong directory	Keep one supported config file at the project root
Styles not applied	Missing virtual CSS import	Add import 'pika.css' outside Nuxt
Cannot find name 'pika'	Generated declarations absent from the TS program	Generate pika.gen.ts and include it, or write it under src
pika is not defined survives into output	Build adapter is missing, disabled, or not scanning the file	Verify the correct bundler adapter and supported extension; update old integrations
Vue transform ordering issue	Old Vite integration	Current Vite adapter uses enforce: 'pre'; update before changing plugin order
Dynamic argument build error	Argument cannot be statically evaluated	Replace runtime values with CSS variables, variant maps, or shortcuts
Local icon collection is ignored	Neutral icons entry used	Import icons from @pikacss/plugin-icons/node
Design-token file source is ignored	Neutral design-tokens entry used	Import designTokens from @pikacss/plugin-design-tokens/node
Plugin config types missing	Augmenting package was never imported	Import and call the plugin factory in pika.config.*
Plugin hook not firing	Factory not called or wrong hook name	Use plugins: [myPlugin()] and exact lifecycle hook names
External plugin data does not trigger reload	Dependency path not registered	Call engine.addConfigDependency(path) in configureEngine

Plugin Development Quick Start

Read references/plugin-development.md before implementing a plugin. Current essentials:

• Hooks are direct methods on defineEnginePlugin({ ... }); there is no setup() wrapper.
• Order is 'pre' → default → 'post'.
• Every hook receives an optional EnginePluginContext; use context.onDiagnostic for structured warnings/errors.
• Use configureRawConfig for defaults and raw config composition.
• Use configureEngine for runtime registration, diagnostics through engine.reportDiagnostic, and external file dependencies through engine.addConfigDependency.
• Extend EngineConfig with TypeScript module augmentation.
• Test with createEngine(config, { onDiagnostic }) and assert diagnostics as data rather than spying on console.

Workflow

Consumer setup

1. Confirm Node.js and bundler versions.
2. Install @pikacss/core plus the correct integration package.
3. Register the bundler plugin or Nuxt module.
4. Add at most one root config file when customization is needed; zero-config defaults are supported.
5. Import pika.css outside Nuxt.
6. Ensure pika.gen.ts exists and is included by TypeScript.
7. Use only supported source extensions and statically analyzable arguments.
8. Load the relevant customization or official-plugin reference before proposing advanced config.

Plugin authoring

1. Define the user-facing behavior and config augmentation.
2. Choose the smallest lifecycle hooks that implement it.
3. Keep platform-specific capabilities behind explicit adapters, such as /node entries.
4. Emit structured diagnostics instead of assuming a console.
5. Register every external file through engine.addConfigDependency.
6. Add createEngine tests for normal behavior, diagnostics, and hook ordering.