If you write code, you've probably seen both camelCase and snake_case. But when should you use each one? This guide covers the conventions used across different programming languages and contexts, with clear rules you can follow.

What is camelCase?

camelCase starts with a lowercase letter, and each subsequent word starts with an uppercase letter — no spaces or underscores.

Examples:

firstName
lastName
getUserProfile
httpResponseCode

What is snake_case?

snake_case uses all lowercase letters with words separated by underscores.

Examples:

first_name
last_name
get_user_profile
http_response_code

When to Use camelCase

Context	Convention	Example
JavaScript variables	camelCase	userName
JavaScript functions	camelCase	calculateTotal()
TypeScript interfaces	PascalCase	UserProfile
Java variables	camelCase	accountBalance
C# properties	PascalCase	FirstName
Swift properties	camelCase	viewController

When to Use snake_case

Context	Convention	Example
Python variables	snake_case	user_name
Python functions	snake_case	calculate_total()
Ruby variables	snake_case	account_balance
PostgreSQL columns	snake_case	created_at
JSON keys (sometimes)	snake_case	first_name
Environment variables	UPPER_SNAKE_CASE	DATABASE_URL
CSS custom properties	kebab-case	--primary-color
URLs/slugs	kebab-case	/blog/my-post

Language-by-Language Guide

JavaScript / TypeScript — camelCase

const firstName = "John";
function getUserProfile() { }
const httpResponseCode = 200;

Python — snake_case

first_name = "John"
def get_user_profile():
    pass
http_response_code = 200

Database Columns — snake_case

CREATE TABLE users (
    first_name VARCHAR(100),
    created_at TIMESTAMP,
    is_active BOOLEAN
);

Quick Conversion

Need to convert between formats? Use CaseShift — a free online tool that converts text to camelCase, snake_case, PascalCase, and more with one click.

Try CaseShift's camelCase converter → | Try snake_case converter →

camelCase vs snake_case — When to Use Each Naming Convention