is experimental: { optimizeCss: true } still in use for nextJS v14.2

[chandra2607]

Summary

We’re using Next.js v14.2 with the App Router. I noticed that experimental: { optimizeCss: true } is no longer mentioned in the official documentation, and it previously relied on the critters package, which is now deprecated.

Just wanted to check — is this setting still in use or has it been removed/handled differently in the newer versions?
https://www.npmjs.com/package/critters
Thanks!

Additional information

No response

Example

No response

[xabierlameiro]

Hi! Great question about experimental.optimizeCss in Next.js v14.2.

Current Status ✅

After checking the Next.js source code, experimental.optimizeCss is still functional in v14.2, even though it's not prominently documented in the current docs.

How it works:

The feature uses Critters under the hood to inline critical CSS and optimize CSS delivery. Here's what I found in the source:

// From next/src/server/config-shared.ts
experimental?: {
  optimizeCss?: boolean | CritersOptions
}

Usage in Next.js v14.2:

// next.config.js
/** @type {import('next').NextConfig} */
const nextConfig = {
  experimental: {
    optimizeCss: true, // or pass Critters options object
  },
}

module.exports = nextConfig

Alternative: inlineCss

There's also a newer experimental.inlineCss option that might be what you're looking for:

const nextConfig = {
  experimental: {
    inlineCss: true,
  },
}

Why it's not in docs:

Experimental features often have limited documentation until they graduate to stable features. The absence from docs doesn't mean it's removed - it's still in the codebase and functional.

Source verification:

• Found in: packages/next/src/server/config-shared.ts
• Used in: packages/next/src/build/webpack/plugins/next-font-manifest-plugin.ts
• Tests exist: test/e2e/app-dir/app-inline-css/

Hope this helps clarify the current status! 🚀