Issue with TailwindCSS JIT (Just-In-Time) Mode Not Purging Unused Styles in Production Build

[edgehue]

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Hi, I'm facing an issue with TailwindCSS's JIT mode not purging unused styles in the production build.
I have followed all the necessary steps to configure Tailwind, including setting the purge option in the tailwind.config.js file, but when I build the project for production, the final CSS file is still too large. The unused classes aren't being purged as expected.

Here is my configuration:

// tailwind.config.js
module.exports = {
  content: [
    "./src/**/*.{html,js,jsx,ts,tsx}",
  ],
  theme: {
    extend: {},
  },
  plugins: [],
}

I'm using Next.js along with TailwindCSS and have tried clearing the cache, restarting the dev server, and rebuilding, but the issue persists.

Steps to Reproduce::

1. Set up a Next.js project with TailwindCSS.
2. Configure the content property in tailwind.config.js to point to all relevant files.
3. Build the project in production mode (next build && next export).
4. Inspect the generated CSS file - it is much larger than expected, containing unused classes.

Expected Behavior:
The production build should purge all unused styles, resulting in a smaller CSS file size.

Actual Behavior:
The unused classes are not purged, and the final CSS file is significantly larger than expected.

Questions:

• Has anyone else encountered this issue with TailwindCSS's JIT mode?
• Are there any additional configurations I need to apply in my tailwind.config.js or Next.js setup?
• Should I manually configure additional purge settings or check for other conflicting plugins?

Looking forward to any suggestions or guidance!

[wlb-tycoon]

Hi! It seems like your tailwind.config.js file is mostly set up correctly, but there might be a couple of things to check to ensure JIT mode and purging are working as expected in production.

1. Check TailwindCSS Version: First, ensure you're using TailwindCSS v2.1 or later. JIT mode is built-in starting from v2.1, but if you're using an older version, you may need to manually enable JIT mode or upgrade Tailwind to the latest version.

You can check the version by running:

npm list tailwindcss

If you need to upgrade:

npm install tailwindcss@latest

2. Ensure Correct Purge Configuration: Starting with Tailwind v3.x, the purge option was replaced by the content key, which you've already set. This is good, but ensure that it correctly includes all the relevant files where Tailwind classes might be used.
   Double-check the file paths for any dynamic class names (e.g., classes generated inside JSX/React or dynamically in templates). Sometimes, the build process can miss files or dynamic content when they aren't explicitly referenced.

Here's an updated version of your config for reference:

module.exports = {
  content: [
    "./pages/**/*.{js,ts,jsx,tsx}",  // Adjust paths based on your project structure
    "./components/**/*.{js,ts,jsx,tsx}",
    "./app/**/*.{js,ts,jsx,tsx}",
  ],
  theme: {
    extend: {},
  },
  plugins: [],
}

3. Ensure the Build Command: Make sure you're running the correct build command for production. In Next.js, the next build command should automatically optimize and purge the unused Tailwind classes in production mode. You can verify this by checking the generated CSS file size after the build and making sure it's minified and optimized.
4. Check for Additional Configuration in Next.js: If you're using Next.js, ensure that you're using the official TailwindCSS plugin. The Next.js documentation recommends the following Tailwind configuration.:

npm install @tailwindcss/forms

and importing Tailwind into your globals.css file like this:

/* globals.css */
@tailwind base;
@tailwind components;
@tailwind utilities;

5. Check for Other Plugins or Custom Configuration: If you're using additional CSS-related plugins (like CSS modules or PostCSS), double-check your configuration to ensure there are no conflicts that might prevent the purge from working correctly. Some setups might interfere with Tailwind's purging mechanism, causing unused classes to persist in the production build.
6. Verify the Production Build Locally: After running next build, try inspecting the final output (in .next/static/css folder for Next.js) to verify if the purging is actually happening. If the file size is still too large, you could manually try cleaning the cache by deleting .next and running the build again:

rm -rf .next
npm run build

Let me know if these suggestions help or if you encounter any other issues!