Set Up Tailwind CSS with TypeScript

Configure Tailwind CSS in TypeScript project with custom theme, utilities, type-safe patterns.

When Use

• Adding Tailwind CSS to existing TypeScript project
• Customizing Tailwind theme for project's design system
• Setting up type-safe component styling patterns
• Configuring Tailwind plugins + extensions

Inputs

• Required: TypeScript project (Next.js, Vite, standalone React)
• Optional: Design system tokens (colors, spacing, fonts)
• Optional: Tailwind plugins to include

Steps

Step 1: Install Tailwind CSS

npm install -D tailwindcss @tailwindcss/postcss postcss

For Next.js (if not already included).

npm install -D tailwindcss postcss autoprefixer
npx tailwindcss init -p

Got: tailwindcss, postcss, autoprefixer installed as dev deps. For Next.js, tailwind.config.ts + postcss.config.js generated by npx tailwindcss init -p.

If fail: npx tailwindcss init fails? Install Tailwind first with npm install -D tailwindcss, retry. Monorepo? Run from app's root dir, not workspace root.

Step 2: Configure tailwind.config.ts

import type { Config } from "tailwindcss";

const config: Config = {
  content: [
    "./src/pages/**/*.{js,ts,jsx,tsx,mdx}",
    "./src/components/**/*.{js,ts,jsx,tsx,mdx}",
    "./src/app/**/*.{js,ts,jsx,tsx,mdx}",
  ],
  theme: {
    extend: {
      colors: {
        primary: {
          50: "#eff6ff",
          100: "#dbeafe",
          500: "#3b82f6",
          600: "#2563eb",
          700: "#1d4ed8",
          900: "#1e3a5f",
        },
        secondary: {
          500: "#6366f1",
          600: "#4f46e5",
        },
      },
      fontFamily: {
        sans: ["Inter", "system-ui", "sans-serif"],
        mono: ["JetBrains Mono", "monospace"],
      },
      spacing: {
        "18": "4.5rem",
        "88": "22rem",
      },
    },
  },
  plugins: [],
};

export default config;

Got: tailwind.config.ts has content array matching project's file locations, custom colors + fonts under theme.extend, proper TypeScript typing with Config import.

If fail: Custom classes do not render? Verify content paths match actual dir structure. Paths are glob patterns relative to project root. Missing paths = Tailwind will not scan those files for class usage.

Step 3: Set Up Global Styles

Edit src/app/globals.css.

@tailwind base;
@tailwind components;
@tailwind utilities;

@layer base {
  html {
    @apply antialiased;
  }

  body {
    @apply bg-white text-gray-900 dark:bg-gray-950 dark:text-gray-100;
  }
}

@layer components {
  .btn-primary {
    @apply bg-primary-600 text-white px-4 py-2 rounded-lg
           hover:bg-primary-700 focus:outline-none focus:ring-2
           focus:ring-primary-500 focus:ring-offset-2
           transition-colors duration-200;
  }
}

Got: globals.css contains three Tailwind directives (@tailwind base, @tailwind components, @tailwind utilities) + any custom base + component layer styles. File imported in root layout.

If fail: Styles not applied? Verify globals.css imported in layout.tsx (or _app.tsx for Pages Router). Check Tailwind directives present + not commented out.

Step 4: Create Type-Safe Utility Helpers

Make src/lib/cn.ts.

import { type ClassValue, clsx } from "clsx";
import { twMerge } from "tailwind-merge";

export function cn(...inputs: ClassValue[]) {
  return twMerge(clsx(inputs));
}

Install deps.

npm install clsx tailwind-merge

Usage in components.

import { cn } from "@/lib/cn";

interface ButtonProps extends React.ButtonHTMLAttributes<HTMLButtonElement> {
  variant?: "primary" | "secondary" | "outline";
}

export function Button({ className, variant = "primary", ...props }: ButtonProps) {
  return (
    <button
      className={cn(
        "px-4 py-2 rounded-lg font-medium transition-colors",
        variant === "primary" && "bg-primary-600 text-white hover:bg-primary-700",
        variant === "secondary" && "bg-secondary-500 text-white hover:bg-secondary-600",
        variant === "outline" && "border border-gray-300 hover:bg-gray-50",
        className
      )}
      {...props}
    />
  );
}

Got: src/lib/cn.ts exports cn() function. clsx + tailwind-merge installed as deps. Components use cn() to merge class names without conflicts.

If fail: clsx or tailwind-merge not found? Run npm install clsx tailwind-merge. TypeScript reports type errors in cn.ts? Verify ClassValue type imported from clsx.

Step 5: Add Dark Mode Support

Update tailwind.config.ts.

const config: Config = {
  darkMode: "class", // or "media" for system preference
  // ... rest of config
};

Toggle implementation.

"use client";
import { useEffect, useState } from "react";

export function ThemeToggle() {
  const [dark, setDark] = useState(false);

  useEffect(() => {
    document.documentElement.classList.toggle("dark", dark);
  }, [dark]);

  return (
    <button onClick={() => setDark(!dark)}>
      {dark ? "Light" : "Dark"} Mode
    </button>
  );
}

Got: Dark mode toggles correctly between light + dark themes. dark class applied to <html> element, dark: prefixed utility classes respond accordingly.

If fail: Dark mode does not toggle? Verify darkMode: "class" set in tailwind.config.ts. Ensure dark class toggled on <html> element (not <body>). For system-preference mode, use darkMode: "media".

Step 6: Add Plugins (Optional)

npm install -D @tailwindcss/typography @tailwindcss/forms

// tailwind.config.ts
import typography from "@tailwindcss/typography";
import forms from "@tailwindcss/forms";

const config: Config = {
  // ...
  plugins: [typography, forms],
};

Got: Plugins installed as dev deps + registered in plugins array of tailwind.config.ts. Plugin-provided classes (prose from typography, styled form elements from forms) available in components.

If fail: Plugin classes do not render? Verify plugin both installed (npm ls @tailwindcss/typography) + added to plugins array. Restart dev server after config changes.

Checks

• Tailwind classes render correctly in browser
• Custom theme values (colors, fonts, spacing) work
• cn() utility merges classes without conflicts
• Dark mode toggles correctly
• TypeScript shows no errors in config or components
• Production build purges unused styles

Pitfalls

• Content paths missing: Classes do not render? Check content array in config matches file locations
• Class conflicts: Use tailwind-merge (via cn()) to prevent conflicting utility classes
• Custom values not working: Ensure custom values under extend (to add) not at theme root (which replaces defaults)
• Dark mode not toggling: Check darkMode setting + that dark class on <html> not <body>

See Also

• scaffold-nextjs-app - project setup before Tailwind config
• deploy-to-vercel - deploy styled application