🔧 Error: Unexpected Token in JSON

The Error Signature

This error triggers when you pass a malformed string into JSON.parse(). Since JSON is a highly strict syntax standard, even a minor discrepancy will crash the parser.

SyntaxError: Unexpected token ' in JSON at position 12
    at JSON.parse (<anonymous>)

Common Causes & Code Examples

1. Single Quotes instead of Double Quotes

JSON does not allow single quotes for keys or string values.

{
  'name': 'Developer',
  "active": true,
}

To fix, replace all single quotes with straight double quotes and remove any trailing commas:

{
  "name": "Developer",
  "active": true
}

2. Unescaped Control Characters

Strings containing real tabs, raw carriage returns, or unescaped forward slashes will fail validation. Use \\n or \\t instead of raw tabs or line breaks inside string values.

3. Trailing Commas

Avoid placing commas after the final key-value pair of an object or the final item of an array list.

Resolution Checklist

• Identify the error position: Copy your JSON string into a text editor, search for the byte/character index indicated in the error message, and inspect that location.
• Validate online: Paste the text into our JSON Formatter tool to automatically highlight the exact line and character causing the syntax breakdown.
• Check smart quotes: Replace any curly quotes like “ or ” with normal straight quotes ".