tailwindcss-debugging

Tailwind CSS Debugging & Troubleshooting

Common Issues & Solutions

1. Styles Not Applying

Check Content Detection

v4 automatically detects content, but if styles are missing:

/* Explicitly specify sources */
@import "tailwindcss";
@source "./src/**/*.{html,js,jsx,ts,tsx,vue,svelte}";

Verify Class Names

<!-- WRONG - Dynamic class won't be detected -->
<div class={`text-${color}-500`}>

<!-- CORRECT - Use complete class names -->
<div class={color === 'blue' ? 'text-blue-500' : 'text-red-500'}>

Check Build Process

# Restart dev server
npm run dev

# Clear cache and rebuild
rm -rf node_modules/.vite
npm run build

2. v4 Migration Issues

PostCSS Plugin Changed

// OLD (v3)
export default {
  plugins: {
    tailwindcss: {},
    autoprefixer: {}
  }
}

// NEW (v4)
export default {
  plugins: {
    '@tailwindcss/postcss': {}
  }
}

Configuration Moved to CSS

/* v4 - Configure in CSS, not JS */
@import "tailwindcss";

@theme {
  --color-primary: oklch(0.6 0.2 250);
}

Dark Mode Variant

/* v4 - Add if using selector strategy */
@custom-variant dark (&:where(.dark, .dark *));

3. Classes Being Overridden

Check Specificity

/* Browser DevTools: Inspect element → Styles panel */
/* Look for crossed-out styles */

Solutions

<!-- Use !important (last resort) -->
<div class="!mt-0">

<!-- Or increase specificity with variants -->
<div class="[&]:mt-0">

Check Import Order

/* Your custom CSS should come after Tailwind */
@import "tailwindcss";
@import "./custom.css";  /* After Tailwind */

4. Typography Plugin Issues

Styles Not Applied

/* Ensure plugin is loaded */
@plugin "@tailwindcss/typography";

Utilities Overridden by Prose

<!-- Use element modifiers -->
<article class="prose prose-h1:text-4xl prose-a:text-blue-600">

<!-- Or escape prose entirely -->
<article class="prose">
  <div class="not-prose">
    <CustomComponent />
  </div>
</article>

5. Forms Plugin Issues

Styles Not Applied to Plain Inputs

<!-- Forms plugin only styles inputs with type attribute -->
<input type="text" />  <!-- ✓ Styled -->
<input />              <!-- ✗ Not styled -->

Using Class Strategy

@plugin "@tailwindcss/forms" {
  strategy: class;
}

<!-- Now explicitly opt-in -->
<input type="text" class="form-input" />

Debugging Tools

VS Code Extension

# Install Tailwind CSS IntelliSense
code --install-extension bradlc.vscode-tailwindcss

Features:

• Autocomplete for class names
• Hover previews showing CSS
• Linting for errors
• Color decorators

Debug Screens Plugin

npm install -D @tailwindcss/debug-screens

@plugin "@tailwindcss/debug-screens";

<!-- Shows current breakpoint in corner -->
<body class="debug-screens">

Browser DevTools

1. Inspect Element → See computed styles
2. Styles Panel → See which rules apply
3. Filter → Search for Tailwind classes
4. Computed Tab → See final computed values

Check Generated CSS

# Output CSS to file for inspection
npx tailwindcss -o output.css --content './src/**/*.{html,js}'

# With verbose logging
DEBUG=tailwindcss:* npm run build

v4 Specific Debugging

Check Plugin Loading

# Look for plugin-related errors
npm run build 2>&1 | grep -i plugin

Verify CSS Variable Output

/* In browser DevTools, check :root for variables */
:root {
  --color-blue-500: oklch(...);
  --spacing-4: 1rem;
}

Content Detection Issues

/* Add explicit sources if auto-detection fails */
@source "./src/**/*.tsx";
@source "./components/**/*.tsx";

/* Exclude paths */
@source not "./src/generated/**";

Common Error Messages

"Cannot find module '@tailwindcss/postcss'"

npm install -D @tailwindcss/postcss

"Unknown at-rule @theme"

Using v3 tooling with v4 syntax. Update your build setup:

npm install -D tailwindcss@latest @tailwindcss/postcss@latest

"Class 'X' doesn't exist"

Dynamic class generation issue:

// BAD
const classes = `bg-${dynamic}-500`

// GOOD
const colorMap = {
  primary: 'bg-blue-500',
  danger: 'bg-red-500'
}
const classes = colorMap[dynamic]

"Styles not updating in development"

# Restart dev server
npm run dev

# Clear Vite cache
rm -rf node_modules/.vite

# Clear Next.js cache
rm -rf .next

Performance Debugging

Large CSS Output

# Check CSS file size
ls -lh dist/assets/*.css

# If too large, check for:
# 1. Dynamic class generation
# 2. Unnecessary safelisting
# 3. Unused plugins

Slow Builds

# Time the build
time npm run build

# v4 should be very fast
# Full build: <1s
# Incremental: microseconds

Debugging Checklist

Initial Setup

• Correct import: @import "tailwindcss";
• PostCSS plugin: @tailwindcss/postcss (not tailwindcss)
• Vite plugin: @tailwindcss/vite (if using Vite)
• CSS file imported in entry point
• Development server restarted after changes

Styles Not Applying

• Class name is complete (no dynamic generation)
• File is in content path
• Browser cache cleared
• No CSS specificity conflicts
• Check DevTools for overridden styles

After Migration

• tailwind.config.js removed or converted
• @theme directive used for customization
• PostCSS config updated
• Dark mode variant added if using selector strategy
• Plugins updated to v4-compatible versions

Production Issues

• NODE_ENV=production
• Build output includes styles
• CSS file linked correctly
• No dynamic class generation issues

Getting Help

Create Minimal Reproduction

# Create fresh project
npm create vite@latest repro -- --template react-ts
cd repro
npm install -D tailwindcss @tailwindcss/vite

# Add minimal code that shows the issue
# Share on GitHub Issues or Discord

Resources

• Official Docs
• GitHub Issues
• Tailwind CSS Discord
• Stack Overflow