Common JSON Syntax Errors and How to Fix Them

Why Does JSON Parsing Fail?

JSON is a strict protocol. A single missing quote, a trailing comma, or a misplaced brace will throw a syntax exception and halt parsing entirely. Let's explore the most frequent errors that developers encounter and how to resolve them.

1. Single Quotes Instead of Double Quotes

JavaScript allows single quotes for strings, but JSON forbids it. All keys and string values must use double quotes.

✕ Error: { 'name': 'John' }

✓ Fix: { "name": "John" }

2. Trailing Commas

JavaScript array syntax is forgiving of trailing commas, but JSON parsing will throw a validation error if the last element inside an array or object has a comma.

// Invalid JSON
{
  "numbers": [1, 2, 3,],
  "address": "NYC",
}

// Valid JSON
{
  "numbers": [1, 2, 3],
  "address": "NYC"
}

3. Unquoted Keys

In standard Javascript objects, keys do not require quotes unless they contain special characters. In JSON, all keys MUST be double-quoted.

✕ Error: { age: 25 }

✓ Fix: { "age": 25 }

4. Missing Commas Between Elements

Forgetting to place a comma between properties in an object or items in an array is a common error when copying and pasting blocks of code.

// Invalid
{
  "firstName": "Tom"
  "lastName": "Hanks"
}

// Valid
{
  "firstName": "Tom",
  "lastName": "Hanks"
}

How to Quickly Fix JSON Errors

If you encounter these errors, you can use our JSON Validator tool to locate the exact line and column where the error lies. Alternatively, our Auto-Repair tool will sweep through common anomalies like single quotes and trailing commas and resolve them instantly.