Migrating from Tailwind CSS v3

Drop-in replacement for Tailwind v3. Same config, same CSS output (after PostCSS normalization). Swap the CLI/plugin and you're done.

With Vite

pnpm remove tailwindcss @tailwindcss/vite
pnpm add -D galeforcecss vite-plugin-galeforcecss

// vite.config.ts
import { defineConfig } from 'vite'
import galeforce from 'vite-plugin-galeforcecss'

export default defineConfig({
  plugins: [
    galeforce({
      content: ['src/**/*.{html,js,jsx,ts,tsx,vue,svelte}'],
    }),
  ],
})

/* src/index.css — unchanged */
@tailwind base;
@tailwind components;
@tailwind utilities;

Your tailwind.config.{js,ts} is read as-is. Tailwind's own resolveConfig does the merge, so default theme + theme.extend behave bit-for-bit identically.

With PostCSS / Tailwind CLI

Flags map 1:1:

# Before
npx tailwindcss -i src/index.css -o dist/output.css --content 'src/**/*.{html,jsx,tsx}'

# After
npx galeforcecss build -i src/index.css -o dist/output.css --content src

--input / -i, --output / -o, --config, --content all unchanged. --watch becomes galeforcecss watch.

What works on day one

• All built-in utilities (margin, padding, sizing, colors, typography, flex, grid, backgrounds, borders, shadows, filters, transforms, interactivity, SVG).
• All variants (pseudo-class, pseudo-element, group/peer, named groups, arbitrary [&>*], aria/data, supports, dark mode in all three forms, responsive, container).
• @tailwind base|components|utilities, @layer, @apply, theme(), @screen, screen().
• Plugins authored against the common surface (addUtilities, matchUtilities, addVariant, …).
• Arbitrary values, opacity modifiers, prefix, important, dark mode.

Validate the swap

Run with --diagnostics diagnostics.json. Empty array = clean migration. For high-confidence validation, diff the CSS output:

pnpm --filter @galeforcecss/conformance exec tsx scripts/galeforcecss-compare.ts --project /path/to/your/app

When to stay on Tailwind

• You're on Tailwind v4. GaleforceCSS is a v3 port and won't follow v4.
• A third-party plugin uses PostCSS container semantics beyond walkRules + modifySelectors. Try a build first — most plugins work.
• You need source maps. Not yet generated; see Unsupported features.