Text Case Converter: Upper, Lower, Title, CamelCase and More

Why Text Case Matters

Every programming language and framework has conventions for naming variables, files, and functions. Using the wrong case can break your code or confuse collaborators.

The Most Common Cases

How to Convert Between Cases

Using ToolboxPro

Visit our Case Converter and:

1. Type or paste your text in the input

2. See all cases simultaneously — live preview as you type

3. Click any result to copy it to your clipboard

4. Works with multi-word phrases — just type naturally with spaces

JavaScript Manual Conversion

// camelCase
"hello world".replace(/(?:^|s+)(\w)/g, (_, c) => c.toUpperCase())
  .replace(/\s+/g, '')
  .replace(/^(.)/, c => c.toLowerCase());
// Result: "helloWorld"

// PascalCase (same as camelCase but first letter uppercase)
"hello world".replace(/(?:^|\s+)(\w)/g, (_, c) => c.toUpperCase())
  .replace(/\s+/g, '');
// Result: "HelloWorld"

// snake_case
"hello world".toLowerCase().replace(/\s+/g, '_');
// Result: "hello_world"

// kebab-case
"hello world".toLowerCase().replace(/\s+/g, '-');
// Result: "hello-world"

// SCREAMING_SNAKE_CASE
"hello world".toUpperCase().replace(/\s+/g, '_');
// Result: "HELLO_WORLD"

// Title Case
"hello world".replace(/\w\S*/g, w => w.charAt(0).toUpperCase() + w.slice(1).toLowerCase());
// Result: "Hello World"

Case Conventions by Language

JavaScript / TypeScript

// camelCase — variables and functions
const userName = "Alice";
function fetchUserData() {}

// PascalCase — classes and components
class UserService {}
function UserCard() {}

// SCREAMING_SNAKE_CASE — constants
const MAX_FILE_SIZE = 10 * 1024 * 1024;

// kebab-case — file names
// user-profile.tsx, api-utils.ts

Python

# snake_case — everything except classes
user_name = "Alice"
def fetch_user_data():

# PascalCase — classes only
class UserService:

# SCREAMING_SNAKE_CASE — constants
MAX_FILE_SIZE = 10 * 1024 * 1024

CSS / HTML

/* kebab-case — CSS classes and IDs */
.user-profile-card {
  background-color: #fff;
  font-family: "Inter", sans-serif;
}

/* camelCase — custom properties (modern CSS) */
:root {
  --primaryColor: #3498db;
  --borderRadius: 8px;
}

Special Cases

Acronyms

There's debate about how to handle acronyms in camelCase:

// Option A: All caps
parseJSON, HTMLParser, fetchURL

// Option B: Camel-cased
parseJson, HtmlParser, fetchUrl

// Both are used. Pick one and be consistent.
// The most common convention:
// JavaScript: camelCase acronyms (parseJson)
// C#: PascalCase acronyms (ParseJSON)

Numbers in Identifiers

// Variables can contain numbers but not start with them
user2, item3_name   // ✅ valid
2user, 3rd_item     // ❌ invalid in most languages

Reserved Words

// Can't use reserved words as variable names
// ❌ let class = "math";
// ✅ let className = "math";
// ❌ let default = "value";
// ✅ let defaultValue = "value";

Common Conversion Mistakes

1. Losing Information

// Converting to lower case loses title case info
"McDonald" → lowercase: "mcdonald" → title case: "Mcdonald" ❌

// Our tool handles edge cases like this with special rules

2. Double Converting

// Already camelCase, converting to snake_case then back
"myVariable" → snake_case: "my_variable" → camelCase: "myVariable" ✅

// But watch out:
"myVariable" → lower case: "myvariable" → camelCase: "myvariable" ❌

3. Locale Issues

// Turkish 'i' and 'I' behave differently
// 'i'.toUpperCase() in Turkish locale → 'İ'
// Our tool uses locale-independent conversion

FAQ

What's the difference between camelCase and PascalCase? PascalCase capitalizes the first letter too: CamelCase vs camelCase. Use PascalCase for classes and React components, camelCase for variables and functions.

Which case should I use for database column names? Most databases use snake_case (user_name, created_at). PostgreSQL convention is snake_case. Some teams use camelCase — be consistent.

Can I convert a whole file? Our tool handles bulk text. Copy your file contents, paste, and all cases appear instantly. For programming files, consider language-specific formatters.

What about CONSTANT_CASE vs UPPER_CASE? They're the same thing — screaming snake case. Both refer to all-caps with underscores between words.

Does case matter in URLs? Most web servers treat URLs as case-sensitive. Use kebab-case (all lowercase, hyphens) for URL paths — it's the recommended convention for SEO and readability.

What case do JSON keys use? JSON has no official convention, but camelCase is most common in JavaScript ecosystems and snake_case in Python ecosystems. Our JSON Formatter can help standardize your JSON keys.