文字ケース変換

The Case Converter switches text between programming cases and natural-language cases in one place, so you do not have to retype a label, variable or heading by hand just to change how it is capitalized.

Conversion happens entirely in your browser, so whatever you paste stays on your device and nothing is uploaded.

It covers UPPERCASE, lowercase, Title Case and Sentence case for prose, plus the cases developers need: camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE and dot.case. Each has its home: camelCase in JavaScript and Java, snake_case in Python and Ruby, kebab-case in CSS and URLs, and CONSTANT_CASE for environment variables.

The clever part is tokenization. The converter first splits your input into words, understanding existing camelCase, snake_case, kebab-case and spaces, and treats acronyms like API or HTTP as single units. So myAPIKey becomes my-api-key, not my-a-p-i-key.

Title Case capitalizes the first letter of each word, which is ideal for headings and labels. Sentence case capitalizes only the first word, like ordinary prose. Note that Title Case here does not apply editorial small-word rules (leaving "of" or "the" lowercase), so check headlines if you follow a specific style guide.

Typical uses include renaming a variable to match a new language's convention, turning a heading into a URL slug, building an environment-variable name from a label, or just cleaning up inconsistent capitalization pasted from elsewhere.