Common JSON Mistakes and How to Avoid Them

The Cost of a Syntax Error

JSON is the foundation of high-performance modern web communication. Yet, despite its simplicity, minor syntax errors are responsible for thousands of hours of downtime and debugging every year. A single misplaced comma or an incorrect quote can bring down an entire system if not handled correctly.

1. The Infamous Trailing Comma

While many modern programming languages (like JavaScript or Python) allow trailing commas at the end of lists or objects, the Official JSON Standard does not.

{
  "name": "Jane Doe",
  "roles": ["admin", "editor",]
}

Adding that final comma will cause standard JSON parsers to throw a syntax error. Use our JSON Validator to catch these before they reach your code.

2. Single Quotes Instead of Double Quotes

Developers coming from JavaScript often make the mistake of using single quotes for property names or string values. In JSON, only double quotes are valid.

{
  'id': 101,
  'status': 'pending'
}

3. Number Precision and Overflow

JSON does not specify a maximum precision for numbers. However, when parsing JSON into JavaScript, all numbers are treated as 64-bit floats. This can lead to precision loss for very large integers (e.g., 64-bit database IDs).

Conclusion

JSON is strict for a reason: universal compatibility. By being aware of these common pitfalls and using professional tools to validate your payloads, you can build more robust and resilient systems.