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fati_theDev
fati_theDev

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# 10 JSON Mistakes Every Developer Makes (And How to Avoid Them)

JSON is everywhere.

Whether you're building REST APIs, working with configuration files, or integrating third-party services, chances are you're dealing with JSON every day.

After building several online developer tools for formatting, validating, comparing, and converting JSON, I've noticed the same mistakes appear over and over again.

Here are the ten most common ones—and how to avoid them.

1. Using Single Quotes Instead of Double Quotes

❌ Invalid

{
  'name': 'John'
}
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✅ Valid

{
  "name": "John"
}
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JSON only accepts double quotes for property names and string values.

2. Leaving a Trailing Comma

❌

{
  "name": "John",
  "age": 25,
}
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✅

{
  "name": "John",
  "age": 25
}
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Many languages allow trailing commas, but JSON does not.

3. Forgetting to Escape Special Characters

Incorrectly escaped strings often cause parsing failures.

Example:

{
  "message": "He said \"Hello\""
}
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4. Mixing Data Types

Avoid this:

{
  "price": "100",
  "stock": 50
}
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If price is numeric, keep it numeric.

{
  "price": 100,
  "stock": 50
}
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Consistent data types make your APIs much easier to consume.

5. Making JSON Hard to Read

This:

{"id":1,"name":"Laptop","price":1200}
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is valid, but difficult to debug.

Pretty-printing JSON saves time when troubleshooting.

6. Deeply Nested Objects

Large nested structures become difficult to maintain.

Instead of nesting everything inside multiple objects, consider flattening your data model where it makes sense.

7. Duplicate Keys 

{
  "name": "Alice",
  "name": "Bob"
}
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Most parsers keep only the last value, which can introduce subtle bugs.

8. Ignoring Validation

Never assume JSON coming from users or external APIs is valid.

Always validate before processing.

9. Not Comparing API Responses

When debugging APIs, it's often helpful to compare two JSON responses side by side to quickly identify changes instead of inspecting hundreds of lines manually.

10. Reformatting JSON Manually

Indentation issues waste time.

Use a formatter instead of editing whitespace yourself.

Helpful Tools

If you're looking for free browser-based tools, I've built a collection that can help with everyday development tasks, including:

  • JSON Formatter & Validator
  • JSON Compare
  • JSON to TypeScript
  • Base64 Encoder & Decoder
  • CSS Formatter
  • JavaScript Obfuscator
  • Box Shadow Generator
  • Zakat Calculator

You can try them here:

https://devtoolsworld.com

No signup is required, and everything runs directly in your browser.

Final Thoughts

JSON looks simple, but small mistakes can lead to frustrating bugs.

Using validation, formatting, and comparison tools can save a surprising amount of debugging time—especially when working with APIs every day.

What JSON mistake has cost you the most time? Share it in the comments.

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