7 Common JSON Mistakes Developers Make (and How to Fix Them)

Darshan P — Thu, 16 Jul 2026 06:22:10 +0000

If you've worked with APIs, configuration files, or web applications, you've almost certainly encountered JSON parsing errors.

Most JSON issues come down to a few common mistakes. Here's how to identify and fix them quickly.

1. Trailing Commas

❌ Invalid

{
  "name": "John",
  "age": 25,
}

✅ Valid

{
  "name": "John",
  "age": 25
}

JSON does not allow trailing commas after the last property or array element.

❌ Invalid

{
  'name': 'John'
}

✅ Valid

{
  "name": "John"
}

JSON requires double quotes for both property names and string values.

❌ Invalid

{
  name: "John"
}

✅ Valid

{
  "name": "John"
}

Unlike JavaScript objects, JSON requires quoted property names.

A missing } or ] is one of the most common causes of parsing failures.

Using a formatter or validator makes these errors much easier to spot.

Characters such as quotes, backslashes, and newlines must be escaped properly.

Example:

{
  "message": "He said \"Hello\""
}

Keep values consistent whenever possible.

{
  "id": 1,
  "active": true,
  "price": 19.99
}

Avoid storing numbers or booleans as strings unless required.

Before sending JSON to an API or saving configuration files, validate it to catch syntax errors early.

A formatter can also improve readability by properly indenting nested objects and arrays.

JSON is simple, but even small syntax mistakes can break an application.

Taking a few seconds to validate and format your JSON can save a lot of debugging time.

If you're looking for a fast, browser-based tool to format, validate, beautify, and minify JSON, you can try JSON Formatter Studio:

Everything runs locally in your browser, so your JSON isn't uploaded to a server.

Thanks for reading! If you have any JSON tips or common mistakes you've encountered, feel free to share them in the comments.