Text Case Converter
Convert text to UPPERCASE, lowercase, Title Case or Sentence case — plus reversed text — with live character counts and one-click copy.
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How It Works
This tool switches text between UPPERCASE, lowercase, Title Case (every word capitalized) and Sentence case (first letter after each period capitalized), plus a fully reversed mode — all instantly, with live character counts as you type. The interesting part is not the buttons; it is that case conversion is not actually a universal, one-size-fits-all operation. It is locale-specific: the rules for which lowercase letter matches which uppercase letter genuinely differ between languages, and a converter built only for English quietly gets other languages wrong.
Turkish is the textbook example: English treats "I" and "i" as one simple pair. Turkish has a four-letter system instead — dotted İ/i and dotless I/ı are two separate letter pairs, not variants of the same letter. JavaScript's default toUpperCase()/toLowerCase() functions apply English/Unicode-default rules, not Turkish ones, so "İstanbul".toLowerCase() in plain JavaScript incorrectly returns "i̇stanbul" — with a stray combining dot — instead of the correct "istanbul". Getting it right requires locale-aware functions such as toLocaleLowerCase with an explicit tr-TR locale tag, which this tool uses for Turkish text. German has its own quirk: lowercase "ß" (eszett) has traditionally become "SS" in uppercase; a capital "ẞ" was added to Unicode only in 2017 and "SS" still dominates in practice.
What to Know Before You Use It
- Title Case here capitalizes every word — the safe default for headings and product names. Editorial style guides that lowercase short words ("of", "the", "and") vary by publication; adjust the handful of exceptions by hand if your house style requires it.
- The classic use case: a paragraph typed with Caps Lock accidentally left on. Paste it, click Sentence case, copy the result — no retyping needed.
- Conversion uses your browser's locale-aware functions, so accented letters (é, ö, ñ, ç) and Turkish İ/ı convert correctly rather than falling back to English-only rules.
- Everything runs in your browser; your text is never uploaded to a server.
Frequently Asked Questions
Why is Turkish case conversion different from English?
English treats "I" and "i" as a single pair. Turkish uses four related letters instead: dotted İ (uppercase) / i (lowercase) and dotless I (uppercase) / ı (lowercase) are two genuinely separate letters, not case variants of each other. A converter using default JavaScript or English rules mixes them up — "İstanbul".toLowerCase() can wrongly produce "i̇stanbul" with a stray dot instead of "istanbul". This tool applies Turkish-specific (tr-TR) locale rules so the conversion matches what a Turkish reader expects.
Does Title Case capitalize small words like "and" or "the"?
This tool capitalizes every word, which is the safest default for headings, titles and product names where consistency matters more than editorial nuance. Style guides that lowercase short connecting words differ from publication to publication — if yours requires it, adjust the handful of exceptions by hand after converting.
Are accented letters like é, ö or ñ converted correctly?
Yes. The tool uses your browser's locale-aware case functions rather than a simplistic ASCII-only swap, so é↔É, ö↔Ö, ñ↔Ñ and other non-English letters convert to their proper counterparts instead of being left unchanged or mangled.
What happens to German ß (eszett) when converting to uppercase?
By long-standing convention, lowercase "ß" becomes "SS" in uppercase, since no widely supported uppercase form existed for most of the 20th century. Unicode added a formal capital "ẞ" in 2017, but "SS" remains the dominant real-world convention and is what most tools, including this one, still produce.
Is my text uploaded to a server when I convert it?
No. Every conversion — uppercase, lowercase, title case, sentence case, and the character/word counters — runs entirely inside your browser using JavaScript. Nothing you paste is transmitted, logged, or stored anywhere.
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