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

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.

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2. Using Single Quotes

❌ Invalid

{
  'name': 'John'
}

✅ Valid

{
  "name": "John"
}

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

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3. Missing Quotes Around Property Names

❌ Invalid

{
  name: "John"
}

✅ Valid

{
  "name": "John"
}

Unlike JavaScript objects, JSON requires quoted property names.

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4. Missing or Extra Brackets

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.

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5. Invalid Escape Characters

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

Example:

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

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6. Mixing Data Types

Keep values consistent whenever possible.

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

Avoid storing numbers or booleans as strings unless required.

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7. Not Validating Before Using JSON

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.

Final Thoughts

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:

👉 https://jsonformatterstudio.com

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.