ByteJSON

Common JSON Errors and How to Fix Them

6 min readJSON & Data

JSON parsing errors are among the most common issues developers face when working with APIs and configuration files. A single missing comma or misplaced quote can break your entire application. This guide covers the most frequent JSON errors, how to identify them, and practical solutions to fix each one.

1. Missing Commas Between Elements

This is the most common JSON error. Every key-value pair in an object and every item in an array must be separated by a comma.

Error Example

{
  "name": "John"
  "age": 30
}

Error: Missing comma after "name" property

Fixed Version

{
  "name": "John",
  "age": 30
}

Solution: Add comma between properties

2. Trailing Commas After Last Element

While JavaScript allows trailing commas, JSON strictly forbids them. A comma after the last element causes a parse error.

Error Example

{
  "items": [1, 2, 3,],
  "name": "test",
}

Error: Trailing commas in array and object

Fixed Version

{
  "items": [1, 2, 3],
  "name": "test"
}

Solution: Remove all trailing commas

3. Using Single Quotes Instead of Double Quotes

JSON specification requires double quotes for all strings and keys. Single quotes are not valid JSON syntax.

Error Example

{
  'name': 'John',
  'city': 'NYC'
}

Error: Single quotes used instead of double quotes

Fixed Version

{
  "name": "John",
  "city": "NYC"
}

Solution: Replace all single quotes with double quotes

4. Unquoted Object Keys

In JavaScript objects, keys can be unquoted, but JSON requires all keys to be wrapped in double quotes.

Error Example

{
  name: "John",
  age: 30
}

Error: Object keys must be quoted

Fixed Version

{
  "name": "John",
  "age": 30
}

Solution: Add double quotes around all keys

5. Missing Quotes on String Values

String values must be enclosed in double quotes. Only numbers, booleans, and null can be unquoted.

Error Example

{
  "status": active,
  "message": hello world
}

Error: String values must be quoted

Fixed Version

{
  "status": "active",
  "message": "hello world"
}

Solution: Quote all string values

6. Unescaped Special Characters

Special characters like newlines, tabs, and quotes inside strings must be escaped with a backslash.

Error Example

{
  "text": "Line 1
Line 2",
  "quote": "He said "hello""
}

Error: Unescaped newline and quotes in strings

Fixed Version

{
  "text": "Line 1\nLine 2",
  "quote": "He said \"hello\""
}

Solution: Use escape sequences for special characters

7. Mismatched or Missing Brackets

Every opening brace or bracket must have a matching closing one. This often happens when manually editing JSON.

Error Example

{
  "users": [
    {"name": "John"},
    {"name": "Jane"
  ]
}

Error: Missing closing brace in second object

Fixed Version

{
  "users": [
    {"name": "John"},
    {"name": "Jane"}
  ]
}

Solution: Ensure all brackets are properly closed

Quick Error Reference

Unexpected token

Usually missing comma or wrong quote type

Unexpected end of input

Missing closing bracket or brace

Expected property name

Unquoted key or missing comma

Unexpected number

String value not quoted

Tools to Debug JSON Errors

Use these free ByteJSON tools to validate and fix your JSON data:

JSON Validator

Get exact line and column numbers for errors

JSON Formatter

Beautify JSON to spot structural issues

JSON Escape

Handle special characters correctly

JSON Minifier

Compress JSON for production use

Prevention Tips

  • Use a JSON validator before deploying to production
  • Generate JSON with proper libraries instead of manual string construction
  • Use an IDE with JSON syntax highlighting and error detection
  • Keep JSON formatted during development to spot errors easily
  • Test API responses with validation tools before integrating
Back to TutorialsTry JSON Validator