Case Converter

What is a case converter?

A case converter is a free online tool that changes the letter case of your text — converting it to UPPERCASE, lowercase, Title Case, Sentence case or aLtErNaTiNg case — and lets you copy the result with one click. You type or paste text once, and all five versions appear side by side and update live as you edit. It saves you from retyping a heading in a different style or fixing capitalisation letter by letter.

This tool sits in the text tools collection alongside the word counter and case-related helpers, and like them it runs fully in your browser.

How does each case conversion work?

Each style applies one precise rule to your text. Here is the exact method behind every option, in plain terms and matching what the widget produces:

• UPPERCASE — every letter is converted to a capital letter. the cat becomes THE CAT.
• lowercase — every letter is converted to a small letter. THE CAT becomes the cat.
• Title Case — the text is first made lowercase, then the first letter of every word is capitalised at each word boundary. the cat becomes The Cat.
• Sentence case — the text is first made lowercase, then the first letter of the whole string and the first letter after every period, question mark or exclamation mark is capitalised. the cat. it sleeps becomes The cat. It sleeps.
• aLtErNaTiNg — characters are capitalised by position: even positions (0, 2, 4…) are lowercase and odd positions (1, 3, 5…) are uppercase, counting from zero. Because spaces and digits have no upper or lower form, they still occupy a position and shift the pattern. the cat becomes tHe cAt.

The first character is at position 0, so in alternating case it is always lowercase — that is why the result starts with a small letter every time.

What does one phrase look like in all five cases?

Here is the converter’s default sentence, the quick brown fox. it jumps!, transformed by each rule. These outputs match the tool exactly.

Case style	Result
UPPERCASE	THE QUICK BROWN FOX. IT JUMPS!
lowercase	the quick brown fox. it jumps!
Title Case	The Quick Brown Fox. It Jumps!
Sentence case	The quick brown fox. It jumps!
aLtErNaTiNg	tHe qUiCk bRoWn fOx. It jUmPs!

Notice how Title Case capitalises every word, while Sentence case only capitalises The and the It that starts the second sentence. In the alternating row, the space and the period each take a position, which is why fOx. is followed by a capital I in It.

Can you show a worked example with a brand name?

Take the input iPhone 13 PRO. buy now!. Because most styles lowercase the text before re-capitalising, the original mixed-case brand and acronym are not preserved. Here is the full breakdown:

Case style	Result
UPPERCASE	IPHONE 13 PRO. BUY NOW!
lowercase	iphone 13 pro. buy now!
Title Case	Iphone 13 Pro. Buy Now!
Sentence case	Iphone 13 pro. Buy now!
aLtErNaTiNg	iPhOnE 13 pRo. BuY NoW!

iPhone becomes Iphone and PRO becomes Pro in Title Case, because the lowercasing step runs first. If you need the genuine brand spelling, copy the closest version and fix those words by hand. In the alternating row the digits 13 and the spaces occupy positions, so the casing pattern picks up again afterward on pRo.

When should you use each case?

Different writing contexts call for different cases. Use this quick guide:

Case style	Best used for
UPPERCASE	Short emphasis, warning labels, abbreviations, button text
lowercase	Usernames, hashtags, URLs, email addresses, code identifiers, tags
Title Case	Headlines, article titles, headings, book and song names
Sentence case	Body copy, descriptions, UI microcopy, captions, email text
aLtErNaTiNg	Playful or sarcastic social posts, memes, stylised display text

Sentence case is the safest default for readable prose because it follows normal writing conventions. Title Case is the standard for headings, though many style guides keep small words like “and”, “of” and “the” lowercase mid-title — a refinement this tool does not apply.

What are common mistakes and limitations?

A few things are worth knowing before you trust the output:

• Acronyms and names are flattened. Every case except aLtErNaTiNg lowercases the text first, so NASA becomes nasa (lowercase) or Nasa (Title Case). Restore those manually.
• Title Case capitalises every word. It does not skip articles, conjunctions or prepositions, so it is “true” title case rather than editorial headline style.
• Sentence boundaries are simple. A new sentence is detected only after ., ! or ?. Abbreviations such as “Dr.” or “U.S.A.” may trigger an unwanted capital on the next word.
• Alternating case counts spaces and punctuation. Because every character holds a position, adding or removing a space can flip the upper/lower pattern of everything after it.
• No undo for the original mix. Once you copy a converted version, the tool cannot reconstruct your original mixed casing — keep a copy if you need it.

For longer documents where you also care about length, pair this with the word counter to check word and character totals after converting.

Is the case converter private and free?

Yes. The case converter is free and runs entirely in your browser — the JavaScript that performs each conversion executes on your own device, so your text is never uploaded, logged or stored on any server. You can use it offline once the page has loaded, paste sensitive content safely, and convert as many phrases as you like. Nothing you type is shared, which makes it suitable for private notes, draft copy and internal text alike. Explore more free text tools when you need to clean up or transform writing.