Common JSON Errors & How to Fix Them

JSON is strict by design. A single misplaced comma or missing quote can break your entire document. Here are the most common JSON errors and how to fix them.

1. Trailing Commas

Unlike JavaScript, JSON does not allow trailing commas after the last item in an object or array.

// ❌ Invalid — trailing comma
{ "name": "John", "age": 30, }

// ✅ Valid
{ "name": "John", "age": 30 }

2. Unquoted Keys

All object keys in JSON must be wrapped in double quotes. Single quotes or bare identifiers are not valid.

// ❌ Invalid — unquoted key
{ name: "John" }

// ❌ Invalid — single quotes
{ 'name': 'John' }

// ✅ Valid
{ "name": "John" }

3. Missing Brackets or Braces

Every object must have a matching closing brace } and every array a matching closing bracket ].

// ❌ Invalid — missing closing brace
{ "items": [1, 2, 3 ]

// ✅ Valid
{ "items": [1, 2, 3] }

4. Single Quotes Instead of Double Quotes

JSON requires double quotes for strings. Single quotes are only valid in JavaScript object literals, not in JSON.

// ❌ Invalid — single quotes
{ "message": 'Hello world' }

// ✅ Valid
{ "message": "Hello world" }

5. Invalid Number Formats

JSON does not allow leading zeros, hexadecimal literals, or special number values like Infinity or NaN.

// ❌ Invalid
{ "value": 01, "hex": 0xFF, "inf": Infinity }

// ✅ Valid
{ "value": 1, "hex": 255, "inf": null }

6. Unescaped Special Characters

Control characters and certain special characters must be escaped in JSON strings using backslash sequences.

// ❌ Invalid — unescaped newline
{ "text": "Hello
World" }

// ✅ Valid
{ "text": "Hello\nWorld" }

How to Debug JSON Errors