What causes "The package.json is malformed" in vuejs/vue-cli?

vuejs/vue-cli · error · Error

The package.json is malformed

Error message

The package.json is malformed

What it means

Thrown by getPackageJson in getPkg.js when the package.json file exists and is readable but fails JSON.parse — meaning the file content is not valid JSON. The catch wraps any parse error (unexpected token, trailing comma, etc.) into this generic message.

Source

Thrown at packages/@vue/cli/lib/util/getPkg.js:20

// See issue #1815

const fs = require('fs')
const path = require('path')

function getPackageJson (projectPath) {
  const packagePath = path.join(projectPath, 'package.json')

  let packageJson
  try {
    packageJson = fs.readFileSync(packagePath, 'utf-8')
  } catch (err) {
    throw new Error(`The package.json file at '${packagePath}' does not exist`)
  }

  try {
    packageJson = JSON.parse(packageJson)
  } catch (err) {
    throw new Error('The package.json is malformed')
  }

  return packageJson
}

module.exports = function getPkg (context) {
  const pkg = getPackageJson(context)
  if (pkg.vuePlugins && pkg.vuePlugins.resolveFrom) {
    return getPackageJson(path.resolve(context, pkg.vuePlugins.resolveFrom))
  }
  return pkg
}

View on GitHub (pinned to 7eb93c169c)

Solutions

Validate the JSON: `node -e "JSON.parse(require('fs').readFileSync('package.json','utf8'))"` or use an online JSON validator.
Common fixes: remove trailing commas, ensure all keys and string values use double quotes, remove comments.
Check for merge conflict markers (<<<<, ====, >>>>) and resolve them.
Run `npm install` — npm itself will often report the exact parse error location.

Example fix

// before (package.json)
{
  "name": "my-app",
  "version": "1.0.0",   <-- trailing comma
}
// after
{
  "name": "my-app",
  "version": "1.0.0"
}

Defensive patterns

Strategy: validation

Validate before calling

const fs = require('fs');
try {
  JSON.parse(fs.readFileSync('package.json', 'utf-8'));
} catch (e) {
  console.error('package.json is invalid JSON:', e.message);
}

Try / catch

try {
  const pkg = getPkg(context);
} catch (e) {
  if (e.message === 'The package.json is malformed') {
    console.error('Fix package.json JSON syntax. Run: node -e "JSON.parse(require(\'fs\').readFileSync(\'package.json\',\'utf8\'))"');
    process.exit(1);
  }
  throw e;
}

Prevention

Validate package.json after manual edits with `npm install` or a JSON linter.
Resolve all git merge conflict markers in package.json.
Use double quotes for all keys and string values, avoid trailing commas and comments.
Consider using an editor with JSON validation/autocomplete.

When it happens

Trigger: Running a Vue CLI command in a project whose package.json contains invalid JSON: unquoted keys, trailing commas, single-quoted strings, comments, or corrupted/truncated content.

Common situations: Manual editing of package.json introduced a syntax error (e.g., trailing comma, missing quote). A merge conflict left conflict markers in the file. A tool or editor accidentally corrupted the file. Copy-pasting from documentation that used JS object shorthand.

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of vuejs/vue-cli@7eb93c169c (2026-08-13). Data as JSON: /api/errors/f4d3aec5fc7f0be5. Report an issue: GitHub.