How to Convert JSON Keys with a Case Converter (Developer's Guide)

JSON (JavaScript Object Notation) is one of the most widely used formats for APIs and data exchange. While JSON itself doesn't enforce key naming rules, different programming languages and teams often follow specific case conventions like camelCase, snake_case, or PascalCase.

If your API expects camelCase but your backend uses snake_case, you'll need to convert JSON keys consistently. This guide explains how to use a case converter for JSON keys with practical examples.

Why Convert JSON Keys?

• Consistency: Keep JSON responses readable and predictable.
• Language standards:
  • JavaScript → camelCase
  • Python → snake_case
  • C# → PascalCase
• API compatibility: Match the expected naming convention of your consumers.
• Automation: Avoid manual renaming of large datasets.

Common Case Styles in JSON

• camelCase → {"userName": "JohnDoe"}
• snake_case → {"user_name": "JohnDoe"}
• PascalCase → {"UserName": "JohnDoe"}
• kebab-case (less common) → {"user-name": "JohnDoe"}

How to Convert JSON Keys

1. Online Case Converters

For small payloads, paste your JSON into our JSON Case Converter. Choose camelCase, snake_case, or PascalCase, and copy the updated result.

2. Using JavaScript

function toCamelCase(str) {
  return str.replace(/([-_][a-z])/g, group =>
    group.toUpperCase().replace('-', '').replace('_', '')
  );
}

function convertKeysToCamel(obj) {
  if (Array.isArray(obj)) {
    return obj.map(v => convertKeysToCamel(v));
  } else if (obj !== null && obj.constructor === Object) {
    return Object.keys(obj).reduce((result, key) => {
      const newKey = toCamelCase(key);
      result[newKey] = convertKeysToCamel(obj[key]);
      return result;
    }, {});
  }
  return obj;
}

const data = { user_name: "John", account_id: 123 };
console.log(convertKeysToCamel(data));
// Output: { userName: "John", accountId: 123 }

3. Using Python

import re

def to_camel_case(s):
    parts = s.split('_')
    return parts[0] + ''.join(word.capitalize() for word in parts[1:])

def convert_keys_to_camel(d):
    if isinstance(d, dict):
        return {to_camel_case(k): convert_keys_to_camel(v) for k, v in d.items()}
    elif isinstance(d, list):
        return [convert_keys_to_camel(i) for i in d]
    else:
        return d

data = {"user_name": "John", "account_id": 123}
print(convert_keys_to_camel(data))
# Output: {'userName': 'John', 'accountId': 123}

4. Using Node.js Libraries

Popular npm packages for case conversion:

• change-case
• camelcase-keys
• snakecase-keys

npm install camelcase-keys

import camelcaseKeys from 'camelcase-keys';

const data = { user_name: 'John', account_id: 123 };
console.log(camelcaseKeys(data));
// Output: { userName: 'John', accountId: 123 }

Best Practices

• Pick one convention per project and stick to it.
• Convert at the API boundary (when sending/receiving data).
• Automate conversions with libraries for consistency.
• Avoid mixed styles to reduce confusion.

Internal Links

Learn about style differences in Camel Case vs Snake Case.

Try our free Case Converter Tool for text and JSON.

Explore Pascal Case Converter for C# naming conventions.

FAQ

1. Why does JSON need case conversion?

To match naming conventions required by specific languages or APIs.

2. Is camelCase standard in JSON?

Yes, camelCase is common in JavaScript and JSON APIs, but not mandatory.

3. Can I convert JSON keys online?

Yes, paste JSON into an online case converter tool.

4. How do I convert JSON keys in Python?

Use custom functions or libraries to transform dictionary keys.

5. What's the difference between camelCase and snake_case in JSON?

camelCase uses capital letters to separate words, snake_case uses underscores.

6. Are there libraries to handle this automatically?

Yes, libraries like camelcase-keys (Node.js) and humps (Python).

7. Will case conversion affect values?

No, only keys are changed, values remain the same.

8. Is PascalCase recommended for JSON?

It's less common, but some C# projects use PascalCase.

9. Can I convert nested JSON objects?

Yes, recursive functions or libraries handle deep conversions.

10. Does case style impact API performance?

No, but it impacts readability and consistency.

Final Thoughts

Converting JSON keys with a case converter ensures consistency, readability, and compatibility across languages. Whether you use an online tool, a custom script, or a dedicated library, the key is to pick a convention (camelCase, snake_case, or PascalCase) and stick with it.