camelCase to snake_case Converter — Free Online Tool for Developers

By Alex Johnson — The case conversion I do most is camelCase to snake_case when mapping JavaScript frontend code to Python backends. I have done it hundreds of times. Here is the complete guide to naming conventions and how to convert between them instantly.

Switching between programming languages and codebases means constantly converting variable names between formats. Python uses snake_case. JavaScript uses camelCase. CSS uses kebab-case. SQL uses snake_case. React components use PascalCase. Getting the casing wrong does not just look bad — in case-sensitive languages, it causes runtime errors and type mismatches that can take an embarrassingly long time to debug.

The complete guide to naming conventions in 2026

Every major programming language and framework has established naming conventions that developers are expected to follow. Using the wrong convention does not always cause errors, but it marks code as written by someone unfamiliar with the ecosystem — and linters will flag it.

camelCase

First word lowercase, subsequent words capitalized. No separators.

Examples: userName, getApiResponse, isLoggedIn, handleSubmitForm

Used in: JavaScript variables and functions (ECMAScript standard), TypeScript, Java variables and methods, Swift variables, Kotlin variables, Go (though Go prefers shorter names), JSON keys (by convention).

With over 17 million JavaScript developers globally, camelCase is arguably the most widely used naming convention in software development.

PascalCase (UpperCamelCase)

Every word capitalized including the first. No separators.

Examples: UserName, ApiResponse, ButtonComponent, DatabaseConnection

Used in: Class names in virtually all object-oriented languages (JavaScript, TypeScript, Java, Python, C#, PHP), React component names, TypeScript type and interface names, C# method names.

snake_case

All lowercase with underscores as word separators.

Examples: user_name, get_api_response, is_logged_in, database_connection

Used in: Python variables, functions, and module names (mandated by PEP 8, followed by 8+ million Python developers), Ruby variables and methods, database column and table names in PostgreSQL, MySQL, and SQLite, file names in Unix/Linux environments.

SCREAMING_SNAKE_CASE (UPPER_SNAKE_CASE)

All uppercase with underscores.

Examples: MAX_RETRY_COUNT, API_BASE_URL, DEFAULT_TIMEOUT_MS

Used in: Constants in Python (PEP 8), JavaScript (ESLint convention for const declarations at module scope), Java static final fields, environment variables in all languages and shells.

kebab-case

All lowercase with hyphens as word separators.

Examples: user-name, api-response, button-component, background-color

Used in: CSS class names and custom properties, HTML attributes and data-* attributes, URL slugs (Google recommends hyphens over underscores for SEO), npm package names, file names in web projects (React, Vue, Angular components are often kebab-cased as files).

When you need to convert between formats

The most common conversion scenarios developers encounter:

API response to JavaScript variables

REST APIs often return JSON with snake_case keys (following Python or Ruby backend conventions): user_first_name, created_at, is_active. JavaScript frontends expect camelCase: userFirstName, createdAt, isActive. When there is no automatic serializer doing this mapping, developers rename properties manually — which is exactly the kind of repetitive task a case converter eliminates.

Database to application layer

SQL columns are conventionally snake_case: first_name, created_at, order_total. ORM models in JavaScript (Sequelize, Prisma, TypeORM) often use camelCase internally. Mapping between layers manually on large schemas is error-prone.

Cross-language projects

Microservices architectures routinely mix Python (snake_case), JavaScript (camelCase), and Go (camelCase with shorter names). Shared data models need to be expressed in multiple formats consistently.

CSS from design tools

Design tools like Figma export component names in Title Case or spaces. CSS requires kebab-case. Converting "Primary Button Large" to primary-button-large for dozens of components is tedious by hand.

How to use the case converter — step by step

1. Go to Virtual Text Tools and click the Case tab
2. Paste your text — can be a single variable, a list of variables, or a block of text
3. Click the target format button: camelCase, snake_case, kebab-case, PascalCase, UPPERCASE, lowercase, Title Case, or Sentence case
4. The result appears instantly in the output box
5. Click Copy result or use the Swap button to chain conversions

Chaining conversions

Sometimes you need to go through an intermediate format. For example, to convert MyClassName (PascalCase) to my-class-name (kebab-case), the cleanest path is: PascalCase → lowercase (gives myclassname) → that does not work. A better approach: PascalCase → snake_case first (the tool inserts underscores at capital letter boundaries), then swap, then convert to kebab-case by replacing underscores with hyphens.

In practice, going through snake_case as an intermediate format works reliably for most conversions because underscores clearly mark word boundaries.

Frequently asked questions

What is the difference between camelCase and PascalCase?

camelCase starts with a lowercase letter: myVariable. PascalCase capitalizes the first letter: MyVariable. camelCase is used for variables and functions in JavaScript. PascalCase is used for classes and React component names.

When should I use snake_case vs camelCase?

Use snake_case for Python variables and functions (PEP 8), database columns, and Unix file names. Use camelCase for JavaScript variables and functions, Java, Swift, and Kotlin. The convention is language-specific — follow whatever is standard for the language or framework you are working in.

Is there a limit on text length?

No. The converter runs in your browser with no server-side processing, so there is no limit. Convert single variable names or entire files.