How to Fix Invalid JSON: Common Syntax Errors

Introduction

JSON is extremely strict. A single incorrect character will cause a SyntaxError and halt execution. In this practical guide, we will analyze the top four errors developers make when drafting JSON files and walk through how to solve them.

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Error 1: Trailing Commas

The Mistake

{
  "name": "Alex",
  "role": "QA",
}

Why it fails: The comma after "QA" implies there is another key/value pair following it.

The Fix

Remove the trailing comma on the final element:

{
  "name": "Alex",
  "role": "QA"
}

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Error 2: Single Quotes for Keys or Values

The Mistake

{
  'id': 456,
  'status': 'pending'
}

Why it fails: JSON specification requires double quotes (") for all keys and string values. Single quotes are syntactically invalid.

The Fix

Swap all single quotes with double quotes:

{
  "id": 456,
  "status": "pending"
}

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Error 3: Unescaped Quotes Inside Strings

The Mistake

{
  "quote": "She said "Hello" to me"
}

Why it fails: The nested double quotes around "Hello" close the string early, confusing the parser.

The Fix

Escape internal quotes using backslashes (\):

{
  "quote": "She said \"Hello\" to me"
}

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Error 4: Unwrapped String Keys

The Mistake

{
  username: "admin"
}

Why it fails: Unlike standard JavaScript objects, JSON keys must be wrapped in double quotes.

The Fix

{
  "username": "admin"
}

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Frequently Asked Questions

Can I run a automatic tool to clean bad JSON?

Yes! Our JSON Editor can help visualize and identify error spots immediately so you can fix them interactively.