camelCase vs snake_case vs kebab-case: Which Should You Use and When?

Naming things is famously one of the hardest problems in programming. Picking the wrong naming convention for the wrong context is a small but persistent source of bugs and confusion.

The Main Naming Conventions

camelCase — each word starts with a capital letter except the first. Used in JavaScript variables/functions, Java, Swift, and JSON keys. Example: getUserData

PascalCase — like camelCase but the first word is also capitalized. Used for class names, React components, and C# types. Example: UserProfile

snake_case — all lowercase, words separated by underscores. Used in Python, Ruby, database columns, and file names. Example: get_user_data

SCREAMING_SNAKE_CASE — all uppercase with underscores. Used for constants and environment variables. Example: API_BASE_URL

kebab-case — all lowercase, words separated by hyphens. Used in HTML attributes, CSS classes, URL slugs, and CLI flags. Example: my-component

Why Mixing Conventions Actually Breaks Things

This isn't just a style preference — it causes real bugs. A common one: a backend API returns JSON with snake_case keys (user_id, created_at) because it's written in Python, but the frontend JavaScript expects camelCase (userId, createdAt) by convention. Without a conversion layer, code silently reads undefined for every field, since data.user_id and data.userId are completely different property names to JavaScript. This exact mismatch is one of the most common integration bugs between Python/Ruby backends and JavaScript frontends.

Where These Conventions Actually Came From

snake_case dates back to early C and Unix conventions, where terminals and compilers had limited character support and readability mattered in fixed-width fonts. camelCase became dominant in Java and later JavaScript partly because it produces shorter identifiers than snake_case, which mattered more as codebases and file sizes grew. kebab-case exists mainly because URLs and CSS class names can't contain underscores as reliably across older browsers and web servers, making hyphens the safer default.

Quick Reference by Context

Convert Between Cases Instantly

Use the Anonymiz Case Converter to convert any text to camelCase, snake_case, kebab-case, PascalCase, SCREAMING_SNAKE_CASE, Title Case, or dot.notation in one click. No signup needed.