camelCase vs snake_case

Every programmer encounters the camelCase vs snake_case debate early in their career. These two naming conventions dominate the programming world, and the choice between them is rarely a matter of personal preference — it is determined by the language, framework, and ecosystem you are working in. This guide covers the conventions used by every major language, readability research, conversion techniques, and the reasoning behind each style.

All Major Naming Conventions

Before comparing camelCase and snake_case, here is a complete overview of all common naming conventions:

Convert between all of these instantly with our Text Case Converter.

Conventions by Programming Language

Notice a near-universal pattern: PascalCase for classes/types and SCREAMING_SNAKE_CASE for constants. The real split between languages is only in variables and functions, where the camelCase vs snake_case divide falls.

camelCase in Detail

camelCase (also called lower camelCase) starts with a lowercase letter and capitalizes the first letter of each subsequent word. There are no separators between words:

// JavaScript / TypeScript
const userName = "alice";
function getUserProfile(userId) { ... }
const isAuthenticated = true;
const handleClickEvent = () => { ... };

// Go (exported functions use PascalCase)
func getBlockNumber() uint64 { ... }
func (c *Client) sendTransaction(tx *Transaction) { ... }

Advantages: Compact (no separator characters), widely used in the web ecosystem, and closely matches how APIs name JSON keys. Go takes this further by using capitalization to control visibility: PascalCase for exported (public) identifiers and camelCase for unexported (private) ones.

Challenges: Acronyms and abbreviations can be awkward. Should it be xmlHTTPRequest, xmlHttpRequest, or XMLHTTPRequest? Style guides differ on this. Single-word boundaries can also be ambiguous: does parsedBToken mean "parsed B-token" or "parse dB token"?

snake_case in Detail

snake_case uses underscores to separate words, with all letters in lowercase:

# Python
user_name = "alice"
def get_user_profile(user_id):
    ...
is_authenticated = True
MAX_RETRIES = 3  # constant uses SCREAMING_SNAKE_CASE

// Rust
let user_name = "alice";
fn get_user_profile(user_id: u64) -> UserProfile { ... }
let is_authenticated = true;
const MAX_RETRIES: u32 = 3;

Advantages: Unambiguous word boundaries (every underscore is a separator), easier to read for newcomers, handles acronyms naturally (parse_xml_http_request), and is arguably easier to read in identifiers with many words.

Challenges: Takes more horizontal space due to underscore characters, requires reaching for the underscore key (shift + hyphen on US keyboards), and looks unfamiliar to developers coming from JavaScript/Java backgrounds.

What Research Says About Readability

Several academic studies have investigated the readability of different naming conventions:

• Binkley et al. (2009): Found that snake_case identifiers were identified more quickly and accurately by programmers with less training, while experienced programmers showed no significant difference.
• Sharif & Maletic (2010): Using eye-tracking, they found that snake_case identifiers required fewer fixations and less time to accurately identify, suggesting lower cognitive load.
• Bonita Sharif (2010): Confirmed that underscored identifiers lead to higher accuracy in correctness of identification, though the speed difference was small.

The practical takeaway: snake_case may have a slight edge in raw readability, but the most important factor is consistency. Mixing conventions within a codebase is far worse than either choice on its own.

The Cross-Language Conversion Problem

A common challenge arises when different parts of your stack use different conventions. Consider a typical web application:

# Python API returns snake_case
{ "user_name": "alice", "created_at": "2026-01-01", "is_active": true }

// JavaScript frontend expects camelCase
{ userName: "alice", createdAt: "2026-01-01", isActive: true }

// Database column names are often snake_case
SELECT user_name, created_at, is_active FROM users;

Solutions include: automatic conversion middleware (like humps in JavaScript or djangorestframework-camel-case), serializer-level transformation, or simply adopting one convention across the entire API boundary. Use our Text Case Converter to quickly convert identifiers between conventions.

Naming in URLs and Files

Outside of code, naming conventions also matter for URLs, file names, and slugs:

• URLs / slugs: kebab-case is the standard (/guides/camelcase-vs-snake-case). URLs are case-insensitive in practice, and hyphens are treated as word separators by search engines. Use our Slugify Tool to generate URL-friendly slugs.
• File names: kebab-case (user-profile.ts) or snake_case (user_profile.py) depending on the language ecosystem. camelCase file names (userProfile.ts) are used in some JavaScript projects.
• Environment variables: SCREAMING_SNAKE_CASE is universal (DATABASE_URL, API_SECRET_KEY).
• CSS: kebab-case is the only convention (background-color, font-size, border-radius). CSS custom properties also use kebab-case (--primary-color).

Best Practices

• Follow your language's convention: Do not use snake_case in JavaScript or camelCase in Python. Your code will look foreign to other developers in that ecosystem.
• Be consistent within a project: Mixing conventions is the worst option. Pick one and enforce it with a linter (ESLint, Pylint, clippy, golint).
• Use a formatter: Prettier, Black, gofmt, and rustfmt enforce consistency automatically.
• Convert at API boundaries: If your backend uses snake_case and frontend uses camelCase, convert at the serialization layer, not in business logic.
• Handle acronyms consistently: Decide on a rule (e.g., treat acronyms as words: httpUrl, not hTTPURL) and document it.

Frequently Asked Questions