Common JSON Errors and How to Fix Them (Missing Commas, Quotes, etc.)

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JSON is strict. Small mistakes can break your API responses or config files. Here are the most common JSON errors and how to fix them fast.

1. Missing commas between properties

Invalid JSON: A comma is missing between the properties.

{
  "name": "Avi"
  "role": "Developer"
}

Corrected JSON:

{
  "name": "Avi",
  "role": "Developer"
}

2. Using single instead of double quotes

Invalid JSON: Keys and string values use single quotes.

{
  'name': 'Avi'
}

Corrected JSON:

{
  "name": "Avi"
}

If a string value itself contains double quotes, backslashes, or newlines, you must escape those characters so the JSON stays valid.

3. Trailing commas

Invalid JSON: The last property has a trailing comma.

{
  "name": "Avi",
}

Corrected JSON:

{
  "name": "Avi"
}

4. Unquoted keys

Invalid JSON: The property name is not in double quotes.

{
  name: "Avi"
}

Corrected JSON:

{
  "name": "Avi"
}

5. Comments in JSON

JSON does not support comments, even though they are convenient. Attempting to add // comment or /* comment */ will break strict JSON parsing.

Invalid JSON:

{
  // user name
  "name": "Avi"
}

Corrected JSON: Remove the comment.

{
  "name": "Avi"
}

Using an online JSON validator

Copy one corrected JSON block above, paste it into the left editor of the JSON Validator, and click Validate. Each corrected block contains one complete JSON value without comment labels. You can also try its invalid example to see the validator's diagnostic message, then validate the correction.

Next steps

Most JSON errors are just small typos. With a good validator and a bit of practice, you’ll be able to fix them in seconds and keep your APIs and configs healthy.

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