Case Converter

How do I change text to uppercase, lowercase or title case?

1. Paste or type your text into the Input box.
2. Pick a style from the Convert to menu: UPPER CASE, lower case, Title Case, Sentence case, camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE or aLtErNaTiNg.
3. Click Convert case, or wait a moment and the output updates on its own.
4. Check the result in the output panel and switch styles as often as you like; the original stays in the Input box.
5. Click Copy output to copy the converted text.

The four writing styles behave the way an editor would expect. UPPER CASE and lower case change every letter. Sentence case capitalises the first letter after each full stop, question mark or exclamation mark and lowercases the rest, so it is the quickest fix for a heading someone typed in capitals. Title Case capitalises each word but keeps the small connecting words (a, an, the, of, and, in, on, to, for) in lower case unless they start the text, which is the convention used by most UK publishers and style guides.

The developer styles split your text into words first, treating spaces, hyphens, underscores and existing capital letters as boundaries, then join them back up. So "user profile image", "user-profile-image" and "UserProfileImage" all become userProfileImage in camelCase, user_profile_image in snake_case and USER_PROFILE_IMAGE in CONSTANT_CASE. That makes the tool useful for renaming variables between languages, turning a page title into a URL slug with kebab-case, or converting a CSS property name to its JavaScript form.

A few edge cases worth knowing. Accented letters such as é and ü are converted correctly because the tool uses Unicode-aware case mapping rather than plain ASCII. Acronyms are not preserved in Title Case, so "nhs guidance" becomes "Nhs Guidance" and needs a quick manual fix. aLtErNaTiNg case simply flips between lower and upper on each letter, ignoring spaces and punctuation.

The conversion runs as plain JavaScript in your browser tab. Your text is never transmitted or stored, so it is fine to paste confidential documents, code or customer data. There is no length limit in practice; a 50,000-word manuscript converts in a fraction of a second, and the output refreshes shortly after you stop typing.

How it works: this tool uses plain JavaScript running in your browser tab. No server is involved, so Kilnfile never sees your file. Last reviewed 20 September 2026.

Frequently asked questions