On Windows environments, Next.js often throws the following during build:
Failed to compile
ERR_UNSUPPORTED_ESM_URL_SCHEME:
Only URLs with a scheme in: file, data, node are supported…
Received protocol 'c:'
This issue frequently appears in Next.js 14.2.0 when CSS loaders trigger Node’s ESM loader to misinterpret a Windows path (C:\…) as an invalid URL scheme. The build then stops entirely.
This article summarizes the real cause and actionable steps to fully resolve it.
■ What’s actually happening
Node’s ESM loader only accepts three URL schemes:
file://, data:, node:
On Windows, a path like C:\App\project is frequently misinterpreted as:
Protocol: "c:"
And the loader immediately rejects it.
Next.js uses css-loader → postcss-loader for global CSS, so the error usually surfaces at:
globals.css.webpack[...] css-loader → postcss-loader
■ Common conditions that trigger the error
- Using Next.js 14.2.0 without updates
- Windows absolute paths leaking into loader pipeline
- Node.js 18 (older ESM loader behavior)
- Turbopack still partially adopted
- Custom Webpack rules touching CSS
■ Fixes (in order of highest success rate)
1. Update Next.js (most important)
This issue is largely resolved in Next 14.2.4+ and 15.x.
npm install next@latest react@latest react-dom@latest
2. Upgrade Node.js
Recommended version: Node 20.11+
Older ESM loaders are more strict and buggy with Windows paths.
3. Update PostCSS & CSS Loader
Mismatch between loader versions causes incorrect URL processing.
npm install -D postcss@latest autoprefixer@latest css-loader@latest
4. Remove problematic Webpack overrides
For example, this rule breaks Next’s default CSS loader chain:
config.module.rules.push({
test: /\.css$/,
type: 'javascript/auto',
})
5. Temporarily disable Turbopack
Some builds break due to experimental processing.
module.exports = {
experimental: { turbo: false }
}
■ Preventing recurrence
- Avoid imports that include
C:\...paths (VSCode sometimes generates them) - Convert to
file:///URLs if absolutely needed - Keep Next.js and Node updated regularly
■ Summary
This issue is ultimately a version mismatch + Windows path interpretation bug.
Updating Next.js, Node.js, and loader packages almost always resolves it immediately.
