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@vltansky/tailwindcss-rtl-first

A Tailwind CSS plugin that provides RTL-first directional utilities. Instead of writing separate LTR and RTL styles, this plugin automatically handles bidirectional layouts by swapping directional properties based on the dir attribute.

Features

  • πŸ”„ Automatic RTL/LTR property swapping for margin, padding, inset, borders, and text alignment
  • 🎯 Uses logical property mappings (e.g., ml-4 becomes margin-right in LTR, margin-left in RTL)
  • ⚑ Works with Tailwind CSS v4
  • 🎨 Supports all Tailwind spacing, color, and sizing scales
  • πŸ“¦ Zero configuration required

Installation

npm install @vltansky/tailwindcss-rtl-first tailwindcss@^4.0.0

Usage

With CSS (Recommended for v4)

Add the plugin to your main CSS file:

@plugin "@vltansky/tailwindcss-rtl-first";
@import "tailwindcss";

With PostCSS

If you're using PostCSS, create a postcss.config.mjs:

export default {
  plugins: {
    "@tailwindcss/postcss": {},
  },
};

HTML Setup

Add the dir attribute to your HTML:

<!-- For LTR (Left-to-Right) languages -->
<html dir="ltr">
  <body>
    <div class="ml-4 mr-8">
      <!-- ml-4 becomes margin-right: 1rem -->
      <!-- mr-8 becomes margin-left: 2rem -->
    </div>
  </body>
</html>

<!-- For RTL (Right-to-Left) languages -->
<html dir="rtl">
  <body>
    <div class="ml-4 mr-8">
      <!-- ml-4 becomes margin-left: 1rem -->
      <!-- mr-8 becomes margin-right: 2rem -->
    </div>
  </body>
</html>

How It Works

The plugin overrides Tailwind's directional utilities to swap left/right properties based on the dir attribute:

Utility Class LTR Behavior RTL Behavior
ml-4 margin-right: 1rem margin-left: 1rem
mr-4 margin-left: 1rem margin-right: 1rem
pl-4 padding-right: 1rem padding-left: 1rem
pr-4 padding-left: 1rem padding-right: 1rem
left-0 right: 0 left: 0
right-0 left: 0 right: 0
text-left text-align: end text-align: left
text-right text-align: start text-align: right
rounded-l border-top-right-radius + border-bottom-right-radius border-top-left-radius + border-bottom-left-radius
rounded-r border-top-left-radius + border-bottom-left-radius border-top-right-radius + border-bottom-right-radius
border-l border-right-width border-left-width
border-r border-left-width border-right-width

Supported Utilities

The plugin provides RTL-aware versions of:

  • Margin: m*, mx, ml, mr
  • Padding: p*, px, pl, pr
  • Inset: inset-x, left, right
  • Scroll Margin: scroll-m*, scroll-mx, scroll-ml, scroll-mr
  • Scroll Padding: scroll-p*, scroll-px, scroll-pl, scroll-pr
  • Border Radius: rounded-* (all directional variants)
  • Border Width: border-x, border-l, border-r
  • Border Color: border-x-*, border-l-*, border-r-*
  • Text Align: text-left, text-right

Tailwind CSS v4 Notes

CSS Variable Approach

In Tailwind v4, the plugin generates both the base utilities and RTL/LTR-scoped versions. The scoped versions use higher specificity (body[dir="rtl"] & and body[dir="ltr"] &) to override the base utilities.

No Core Plugin Disabling

Unlike v3, Tailwind v4 doesn't support disabling core plugins via configuration. The plugin works by generating additional utilities with higher specificity that override the default behavior.

Cascade Behavior

Because v4 generates both base utilities and RTL/LTR-scoped versions, both properties may be set on an element. For example, ml-4 will generate:

.ml-4 {
  margin-left: 1rem; /* Base Tailwind utility */
}

body[dir="ltr"] .ml-4 {
  margin-right: 1rem; /* RTL-first override */
}

body[dir="rtl"] .ml-4 {
  margin-left: 1rem; /* RTL-first override */
}

The scoped versions win due to higher specificity, but both sides of the margin are technically set. This is generally not an issue, but if you need strict single-side properties, see the Advanced Usage section below.

Advanced Usage

Strict Reset Mode (Optional)

If you need to ensure only one side of a property is set (zeroing the opposite side), you can add this CSS to your project:

@layer utilities {
  /* Reset opposite margins for RTL utilities */
  body[dir="ltr"] .ml-1,
  body[dir="ltr"] .ml-2,
  body[dir="ltr"] .ml-3,
  body[dir="ltr"] .ml-4,
  body[dir="ltr"] .ml-5,
  body[dir="ltr"] .ml-6,
  body[dir="ltr"] .ml-8,
  body[dir="ltr"] .ml-10,
  body[dir="ltr"] .ml-12,
  body[dir="ltr"] .ml-16,
  body[dir="ltr"] .ml-20,
  body[dir="ltr"] .ml-24 {
    margin-left: 0 !important;
  }

  body[dir="rtl"] .ml-1,
  body[dir="rtl"] .ml-2,
  body[dir="rtl"] .ml-3,
  body[dir="rtl"] .ml-4,
  body[dir="rtl"] .ml-5,
  body[dir="rtl"] .ml-6,
  body[dir="rtl"] .ml-8,
  body[dir="rtl"] .ml-10,
  body[dir="rtl"] .ml-12,
  body[dir="rtl"] .ml-16,
  body[dir="rtl"] .ml-20,
  body[dir="rtl"] .ml-24 {
    margin-right: 0 !important;
  }

  /* Repeat for mr-*, pl-*, pr-*, etc. */
}

Note: This is rarely needed and adds CSS bloat. The default behavior (both sides set with correct specificity) works correctly for virtually all use cases.

Testing

Run the unit test suite:

npm test

Run end-to-end test (separate from unit tests, verifies actual CSS generation with v4):

npm run test:e2e

Note: The E2E test runs outside Jest and directly tests the Tailwind v4 compilation pipeline.

Example

<!DOCTYPE html>
<html dir="ltr">
  <head>
    <link href="/dist/output.css" rel="stylesheet" />
  </head>
  <body>
    <div class="flex">
      <!-- In LTR: margin-right: 1rem -->
      <!-- In RTL: margin-left: 1rem -->
      <div class="ml-4">Content</div>

      <!-- In LTR: padding-left: 2rem -->
      <!-- In RTL: padding-right: 2rem -->
      <div class="pr-8">Content</div>

      <!-- In LTR: text-align: end -->
      <!-- In RTL: text-align: left -->
      <p class="text-left">Text</p>
    </div>
  </body>
</html>

Migration from v3

If you're upgrading from a v3-compatible version:

  1. Update to Tailwind CSS v4
  2. Remove corePlugins configuration (no longer needed)
  3. Use @plugin directive in CSS instead of JavaScript config
  4. Test your layouts - the behavior should be identical

License

MIT

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

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