Case Converter

Renaming a hundred variables from camelCase to snake_case, normalizing inconsistent title case across a content list, or converting a column of names to all-caps — each one is a thirty-second job by hand only if there are five entries. At any meaningful volume, the keyboard time adds up to real friction.

Paste text, pick a target case, get the converted output. The supported cases are uppercase, lowercase, title case, sentence case, camelCase, snake_case, kebab-case, and PascalCase. Each follows its standard conventions — title case capitalizes the first letter of major words but not articles or short prepositions; camelCase strips spaces and lowercases the first character; snake_case uses underscores; kebab-case uses hyphens.

Mostly used by developers normalizing variable names from one codebase convention to another, and by writers cleaning up content imported from sources with inconsistent capitalization. The conversion is reversible enough that you can experiment without permanent loss.

The specific rules each case follows: uppercase converts every letter to uppercase, locale-aware in some implementations (the Turkish dotless i is the famous edge case where naive ASCII-only uppercasing breaks). Lowercase is the inverse. Title case capitalizes major words and skips articles, conjunctions, and prepositions of a chosen length — AP style skips words of 3 or fewer letters when not at start or end; Chicago style skips a longer list. Sentence case capitalizes only the first letter and proper nouns, which the tool can't perfectly identify (proper noun detection requires understanding of context). camelCase removes word separators and lowercases the first character; PascalCase does the same but capitalizes everywhere. snake_case and kebab-case insert separators between words and lowercase everything.

Worked example: input "the quick brown fox jumps over the lazy dog". Title case (AP): "The Quick Brown Fox Jumps Over the Lazy Dog" — note "over" capitalized (4 letters) but "the" not. Sentence case: "The quick brown fox jumps over the lazy dog". camelCase: "theQuickBrownFoxJumpsOverTheLazyDog". snake_case: "the_quick_brown_fox_jumps_over_the_lazy_dog". The conversions are deterministic for this clean input. Mixed-script or punctuation-heavy input introduces edge cases the tool handles via documented conventions, not magic.

Limits worth flagging: the tool is locale-naive in the sense that it follows English conventions for what counts as a word boundary and what counts as a "short" preposition. Title case for non-English languages follows different rules (German capitalizes nouns regardless of position, French uses sentence case for titles in many style guides). Acronym handling is the trickiest case — "HTTPParser" should become "http_parser" in snake_case but a strict word-boundary algorithm produces "h_t_t_p_parser". Different style guides treat acronyms as one word or as separate letters; the tool follows Google's JavaScript style guide convention (acronyms as one word) by default.

For codebase-wide renames, the tool is a one-off helper. Real code refactoring needs language-aware tools (TypeScript's rename symbol, Python's rope, Ruby's rubocop) that understand scoping and references. The case converter handles the surface transformation; the harder problem is updating all the call sites without breaking anything. For data cleanup (column normalization, data migration), the tool's bulk conversion is exactly what's needed.