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Guide

A field guide to text casing conventions.

Casing — how you capitalize and join words — is one of the quietest but most important conventions in programming and writing. The right case makes code readable, satisfies linters, and matches the expectations of the language you’re working in. Here’s what each style means and when to reach for it.

Natural-language cases

• UPPERCASE — every letter capitalized. Used for emphasis, headers, or acronyms.
• lowercase — no capitals. Common for tags, slugs, and casual text.
• Title Case — first letter of each word capitalized. Used for headings and titles.
• Sentence case — only the first word of each sentence capitalized. The standard for body text and UI copy.

Programmer cases

• camelCase (helloWorld) — variables and functions in JavaScript, Java, and C#.
• PascalCase (HelloWorld) — classes, types, React components, and interfaces.
• snake_case (hello_world) — variables and functions in Python and Ruby; SQL columns.
• kebab-case (hello-world) — URLs, CSS classes, file names, and HTML attributes.
• CONSTANT_CASE (HELLO_WORLD) — constants and environment variables, everywhere.
• Dot (hello.world) and Path (hello/world) — object access, namespaces, and file paths.

camelCase vs snake_case: which should you use?

Neither is objectively better — what matters is following the convention of your language and team. JavaScript and Java codebases lean on camelCase; Python and Ruby standardize on snake_case (it’s even baked into PEP 8). Databases often use snake_case for column names regardless of the app language. When in doubt, match the surrounding code so the casing stays consistent across the project.

Why consistent casing matters

Consistent casing reduces cognitive load, prevents subtle bugs (in case-sensitive languages, userId and userid are different identifiers), and keeps linters and formatters quiet. For URLs and file names, lowercase kebab-case avoids cross-platform and case-sensitivity issues on servers.

Disclaimer: This tool is provided for convenience and runs entirely in your browser. Conversions are best-effort and follow common conventions; always verify output against your project’s style guide and linter rules before committing.