Text Case Converter

Where this actually comes up: the boundary between two naming conventions

The case I reach for this most isn't renaming a single variable — it's the boundary where two naming conventions meet. A .NET API following Microsoft's PascalCase convention serving JSON to a JavaScript frontend that expects camelCase; a Python service with snake_case fields feeding a C# client that wants PascalCase properties; an environment variable in UPPER_SNAKE_CASE that needs to become a kebab-case command-line flag for a Docker Compose file. Converting one identifier by hand is trivial. Converting twenty of them consistently, by eye, without introducing a typo in one of them, is exactly tedious enough to be worth a tool.

Naming conventions by language and context

The choice of naming convention is not arbitrary — each language community has established conventions that compilers, linters, and developers all expect:

• camelCase — first word lowercase, subsequent words capitalised: getUserName. Used for: JavaScript/TypeScript variables and functions, Java variables and methods, Swift variables and functions, JSON property names in APIs.
• PascalCase (UpperCamelCase) — every word capitalised: GetUserName. Used for: C# classes, methods, and properties (Microsoft's .NET conventions), TypeScript interfaces and types, React component names, Python class names.
• snake_case — all lowercase, words separated by underscores: get_user_name. Used for: Python variables, functions, and module names (PEP 8), Ruby methods and variables, SQL column names, Django model fields, C/C++ function names in system libraries.
• kebab-case — all lowercase, words separated by hyphens: get-user-name. Used for: CSS class names and custom properties, HTML attributes, URL slugs, npm package names, command-line flags.
• UPPER_SNAKE_CASE (SCREAMING_SNAKE_CASE) — all uppercase, words separated by underscores: GET_USER_NAME. Used for: constants in Python (MAX_RETRIES = 3), environment variables (DATABASE_URL), C/C++ preprocessor macros, Java constants (static final).

How to use this tool

1. Type or paste your text into the input field — it can be in any case format or plain words.
2. All five case formats update instantly in the output panel.
3. Click the copy icon next to the format you need.

How digits are handled in a word split

Word-boundary detection runs in passes: first a lowercase-to-uppercase boundary (userName → "user" + "Name"), then a run of capitals followed by a capital-plus-lowercase (parseHTMLTag → "parse" + "HTML" + "Tag"), then a boundary is inserted on either side of any digit run sitting next to a letter. That last pass is what keeps a digit from merging two words together: user2Name splits into "user", "2", and "Name" — giving user_2_name for snake_case, user-2-name for kebab-case, and user2Name unchanged for camelCase, since the digit already sat at a natural boundary. The digit itself is always kept as its own segment rather than being merged into the word on either side.

Consistency matters more than preference

In a team project, consistent naming is more important than which convention you choose. Inconsistent naming — mixing getUserName with get_user_name in the same codebase — slows down code reading, makes autocomplete less useful, and causes subtle bugs when field names need to match an external format like a database schema or JSON API. Most teams enforce naming conventions automatically using linters: ESLint for JavaScript/TypeScript, pylint or flake8 for Python, dotnet format for C#, and stylelint for CSS.

ASP.NET Core's own default JSON serialization is a built-in example of exactly this conversion happening automatically: System.Text.Json's default web defaults apply a camelCase naming policy to outgoing JSON, so a C# property named UserName on a DTO serializes as userName in the API response without you writing any conversion code. That's the same camelCase transform this tool performs by hand — useful to know if you're ever debugging why a property name looks different in the network tab than it does in your C# source.