Letter case converter

Convert text to UPPER, lower, Title or sentence case.

A paragraph typed with caps lock on. A product list exported entirely in lowercase. A set of headings where every word needs a capital. Retyping any of these by hand is slow and easy to get wrong halfway through. Paste the text, pick one of four buttons, and the whole block changes at once.

How it works

The four modes

Each button rewrites the input into the output box. Using hello world. nice day. as the input:

Button	Result
UPPERCASE	HELLO WORLD. NICE DAY.
lowercase	hello world. nice day.
Title Case	Hello World. Nice Day.
Sentence case	Hello world. Nice day.

Title Case vs Sentence case

Title Case capitalises the first letter of every word separated by a space, which suits headings, menu labels and name lists. Sentence case capitalises only the first letter of the text and the first letter after a period, question mark or exclamation mark, leaving everything else lowercase — the right choice for body paragraphs.

Note that Title Case here capitalises every word, including short ones such as of, and and the. Editorial style guides usually keep those lowercase, so a headline may still need a manual pass.

How to use it

Paste your English text into the input box.
Press one of the four buttons.
Press Copy result to take the output.

The original stays in the input box, so you can try a different mode on the same text and compare.

One thing to watch

Every mode except UPPERCASE lowercases the whole string first, then re-capitalises by rule. Names that carry internal capitals — iPhone, NASA, McDonald, PostgreSQL — will not survive intact and need fixing afterwards. The conversion also targets the Latin alphabet; text in scripts without letter case passes through unchanged.

Terms explained

UPPERCASE: Every letter raised to its capital form. Often used for short labels, rarely for running text.
lowercase: Every letter lowered. Useful for normalising imported data before comparing or sorting it.
Title Case: The first letter of each space-separated word capitalised. Suits headings and short labels.
Sentence case: Only the first letter of the text and of each sentence capitalised. Suits paragraphs.
Sentence boundary: The point after a period, question mark or exclamation mark where this tool starts a new capital.

Frequently asked questions

Why did iPhone become Iphone?

Title Case and Sentence case lowercase the entire text first, then capitalise by rule, so any capital in the middle of a word is lost. Names such as iPhone, eBay, NASA and PostgreSQL need to be corrected by hand after conversion. If you only need everything lowered or raised, the UPPERCASE and lowercase buttons do not have this issue.

Does Title Case follow AP or Chicago style?

No. It capitalises every word, while both AP and Chicago keep short prepositions, articles and conjunctions lowercase unless they start the title. Treat the output as a starting point and lowercase words like of, in, and, or the as your style guide requires.

Does it work on languages other than English?

Only for scripts that have upper and lower case, which mainly means the Latin, Greek and Cyrillic alphabets. Korean, Japanese, Chinese, Arabic and Hebrew have no letter case, so that text passes through unchanged. Mixed text is safe — the non-cased parts are simply left alone.

Is there a size limit on the text?

There is no fixed limit, but everything runs in your browser, so a very large block may take a moment on a slower device. For anything book-length, convert it in sections.

Can I undo a conversion?

The input box is never modified, so your original is still there. Press a different button to replace the output, or clear the output box and start again.