What the case converter does
The tool rewrites the letter case of your text in the mode you choose and updates the result as you type. Six modes are available: UPPER CASE, lower case, Word Capitals, Sentence case, aLtErNaTiNg and inverted case. Typical jobs are fixing headings typed in capitals, preparing menu labels and product names, or cleaning up exported spreadsheet text.
Most online converters apply English rules only, so “istanbul” becomes “ISTANBUL”. With Turkish selected as the analysis language, this tool produces “İSTANBUL”. The analysis language is independent of the page language: it defaults to Turkish even on this English page, and you can switch to English rules for English text.
How to use
- Type or paste text into the input field; the result appears after 150 ms.
- Pick a conversion mode; the result refreshes immediately.
- Choose the analysis language: Turkish rules for Turkish text, English rules for English text.
- In Word Capitals mode you can keep short words such as “and, of” or Turkish “ve, ile” lower-case.
- Add brand names and acronyms to “Words to keep as typed”, for example
iPhone, SEO, YouTube. - Copy the result, download it as
.txt, or create a share link.
Including inputs in the share link is off by default. If you enable it, the text is stored after the # in the link and anyone who receives it can read it.
Turkish dotted and dotless I
Turkish has two separate letters: dotted i with the capital İ, and dotless ı with the capital I. English rules map i to I and lower-case İ to i plus a combining dot. In Turkish mode the tool uses toLocaleUpperCase("tr-TR") and toLocaleLowerCase("tr-TR") after NFC normalisation.
| Input | Mode | Turkish rules | English rules |
|---|---|---|---|
| istanbul ışık | UPPER | İSTANBUL IŞIK | ISTANBUL IŞIK |
| I İ | lower | ı i | i and i + combining dot (U+0307) |
| ilk ırmak | Word Capitals | İlk Irmak | Ilk Irmak |
Some letters, such as German ß, become two letters (SS) in upper case, so the output can be longer than the input.
Word and sentence modes
Word Capitals mode capitalises the first letter of every word and lower-cases the rest. A suffix after an apostrophe does not start a new word, which matters for Turkish: “İSTANBUL’DA” becomes “İstanbul’da”, not “İstanbul’Da”. A hyphen does: “çok-yönlü” becomes “Çok-Yönlü”.
This mode makes no claim about editorial title-case rules. The short-word option keeps a fixed list lower-case, except for the first word of a line and the word after a colon.
Sentence case lower-cases the whole text, then capitalises the first letter of the text, of each line and after ., !, ? or … followed by whitespace. Dots inside 3.5 or example.com do not end a sentence, and closing quotes are skipped. Alternating mode switches case letter by letter; inverted mode flips the case of every letter.
Handling proper names
Because sentence case lower-cases the body, names and acronyms such as “Ankara”, “Yunus Emre” or “SEO” are lower-cased as well. The tool does not detect proper names; instead you list the words to protect. In Word Capitals and Sentence case modes each listed word is output exactly as you typed it. Matching ignores case and the dotted/dotless distinction, so iPhone matches “IPHONE”, “iphone” and “İPHONE”.
The list matches single words, so add “Yunus” and “Emre” separately. Inflected Turkish forms must be listed too: İzmir does not match “İZMİR’DE”, but İzmir’de does. The list is ignored in upper, lower, alternating and inverted modes, which apply one rule to the whole text.
Example and interpretation
The heading below was typed in capitals in a CMS entry. It was converted with Turkish rules, Word Capitals and the short-word option: first without a keep list, then with iPhone, Android, SEO, İstanbul’da:
Input : IPHONE VE ANDROID İÇİN SEO İPUÇLARI: İSTANBUL’DA YEREL ARAMA
No keep list : Iphone ve Androıd İçin Seo İpuçları: İstanbul’da Yerel Arama
With keep list : iPhone ve Android İçin SEO İpuçları: İstanbul’da Yerel Arama
Sentence + list: iPhone ve Android için SEO ipuçları: İstanbul’da yerel aramaThe “Androıd” error in the first result follows directly from Turkish rules: the input used an ASCII capital I, which Turkish lower-casing turns into dotless ı. That is right for Turkish words but wrong for foreign brands. The keep list leaves those words as typed and protects the acronym “SEO”. The last line uses sentence case; because İstanbul’da is also listed, the name kept its capital. Always read the result before publishing it.
Limits and privacy
- Up to 100,000 characters (Unicode code points); split longer text.
- No spell checking, proper-name detection or grammar correction; only letter case changes.
- Emoji, flags and combined characters are handled as grapheme clusters and never split.
- Punctuation, spaces, tabs and line breaks are preserved;
- Text is not sent to a server or written to browser storage. It travels in a share link only if you include inputs.
Frequently asked questions
Why does “i” become “İ” in upper case?
In Turkish the capital of dotted i is İ and the capital of dotless ı is I. With Turkish as the analysis language the tool applies that mapping. Switch the analysis language to English for English text.
Why is Turkish the default on the English page?
The tool was built to solve the Turkish İ/ı problem. The page language sets the interface; change the analysis language for English text.
Does Word Capitals mode follow title-case style guides?
No. It capitalises the first letter of each word and can keep a fixed list of short words lower-case. Check the result against your style guide.
Why were names lower-cased in sentence case?
Sentence case lower-cases the body and cannot recognise names. Add them to “Words to keep as typed”.
Is my text saved anywhere?
No. The conversion runs in your browser; the text is not sent to a server and is not stored automatically.