Fixing Module Parse Errors Caused by Bad Escape Sequences in Next.js

Fixing “Module parse failed: Bad character escape sequence” in Next.js

This error occurs frequently on Windows, especially in Next.js 14–15, and is caused by how Webpack parses file paths containing backslashes (\\). These backslashes get interpreted as escape sequences, leading to invalid JavaScript deep inside Next.js loaders.

Below is an improved, expanded, and more complete guide with additional solutions and explanations.

The Error

Module parse failed: Bad character escape sequence

In the logs:

throw new Error('File size for Open Graph image "C:\\Users\\test\\project\\src\\app\\favicon.ico" exceeds 8MB.')

Webpack interprets sequences like \U, \t, \p as escape characters, causing syntax errors.

Why This Happens

Windows paths:

C:\Users\myUser\project

Webpack expects paths to be:

C:/Users/myUser/project

or properly escaped:

C:\\Users\\myUser\\project

When a loader (like next-metadata-route-loader) inserts an unescaped Windows path into a JavaScript string literal, Webpack fails.

1. Remove or Replace favicon.ico

Many developers confirmed that src/app/favicon.ico being processed by Next.js metadata loader caused the crash.

Try:

rm src/app/favicon.ico

Restart:

npm run dev

Then later place a favicon into /public/favicon.ico.

2. Clear the .next Cache

The metadata cache often contains incorrectly escaped paths.

npx rimraf .next
npm run dev

This alone fixes the issue for many.

3. Normalize Windows Paths Manually

If your code or config generates paths, normalize them:

function fixPath(p) {
  return p.replace(/\\/g, '/');
}

Use this when passing paths to loaders or Webpack configuration.

4. Patch or Adjust Webpack Configuration

If a loader emits raw Windows paths, you can override handling:

module.exports = {
  webpack(config) {
    config.module.rules.push({
      test: /\.ico$/,
      type: 'asset/resource',
    });
    return config;
  }
};

Disable verbose path info:

config.output.pathinfo = false;

This prevents Webpack from inserting unescaped paths into comments.

5. Temporarily Disable Metadata Route Processing

You can bypass the problematic loader:

export const dynamic = "force-static";
export const metadata = {};

If the error disappears, the issue is tied to metadata image handling.

6. Ensure Files Are UTF‑8 Encoded

Incorrect encodings can produce malformed byte sequences Webpack cannot parse.

7. Upgrade Next.js + Webpack

Many Windows path-escaping bugs were fixed after:

npm install next@latest
npm install webpack@latest

Next.js 15 includes improved Windows support.

8. Patch the Broken Loader (Permanent Fix)

If the issue is inside Next.js internals, patch the loader:

npm install patch-package

Modify:

node_modules/next/dist/build/webpack/loaders/next-metadata-route-loader.js

Change:

"..." + filePath + "..."

to:

"..." + filePath.replace(/\\/g, "\\\\") + "..."

Then save a patch:

npx patch-package next

This ensures every backslash is escaped properly.

Summary