Lowercase to Uppercase Converter

Five modes, and when each one fits

Case changes are small edits with large effects. A headline in Title Case reads like a headline. The same words in sentence case read like a sentence. A form field in UPPER reads like a shout, and a shared file name in UPPER reads like an accident.

This converter offers five modes. Pick one from the menu and the result appears as you type. Nothing is sent anywhere, and the copy button puts the output on your clipboard.

The menu also shows a live character count and word count. Case rarely changes the count, but when it does, the counter shows you.

UPPER and lower: the two that look simple

UPPER and lower are a character by character map defined by Unicode. Every lowercase letter has an uppercase partner, and the mapping runs both ways. The letters a to z and A to Z are the easy part. Accented letters, Greek, Cyrillic and the rest follow the same rule with their own partners.

In most cases the length stays the same. An 11 character string in lower is still 11 characters in UPPER. German ß breaks that rule: it has no single uppercase letter, so UPPER writes SS and the string grows from 6 characters to 7. The word straße becomes STRASSE.

lower is the safer direction when you compare text. If two strings differ only in case, lower makes them equal, which is why email addresses and tags are stored that way. UPPER is better for anything a person has to spot from across a room: serial numbers, warning labels, the headings on a paper form.

One warning. Do not run UPPER on text you plan to search later unless the search is case blind, because a stored HELLO and a typed hello do not always match.

Title Case: the small words that stay down

Title Case capitalizes the first letter of each important word. The first and last word of the title always count as important, even when they are small. Everything in between follows one rule: small words stay lowercase, the rest get a capital.

The small words are articles, conjunctions and short prepositions. They carry little meaning on their own, and a title that capitalizes all of them looks lumpy.

Take a 9 word headline: a guide to the best coffee shops in town. That is 40 characters. Title Case gives A Guide to the Best Coffee Shops in Town, with 6 words capitalized and 3 left down.

Hyphenated words get a capital on each part, so state-of-the-art becomes State-of-the-Art, except when the middle part is a small word and your style guide says to leave it down. Words that already carry capitals are left alone, which is how iPhone, eBay and NASA survive the trip. The catch is that a lowercase acronym cannot be rescued: type usa and you get Usa, so put the caps in first.

Style guides disagree at the edges. The Associated Press capitalizes every word of 4 or more letters. The Chicago Manual of Style lowercases prepositions no matter how long they are. This tool follows the short word list above. When a client hands you a house style, follow the client.

Sentence case: what it gets wrong

Sentence case lowercases the whole string, then puts a capital on the first letter of each sentence and on the pronoun I. It is the shape of ordinary writing, which is why it suits body copy, captions and button labels.

The method has one blind spot: it cannot know which words are names. Run it on the iphone and the usa shipped in may and you get The iphone and the usa shipped in may. The first letter is fixed because it opens the sentence, and the three proper nouns stay flat.

That blind spot is easy to live with when you are cleaning a spreadsheet full of SHOUTED product names, and a problem when the text goes to print. Read the output once and fix the names by hand.

Sentence case also has to guess where sentences end. It treats a period, a question mark and an exclamation mark as ends, so a decimal like 3.5 or an abbreviation like Dr. can trigger a capital that does not belong. The tool only capitalizes a letter that follows the mark, so 3.5 stays intact, but Dr. smith becomes Dr. Smith. Check those two patterns in your text.

tOGGLE and the characters that refuse to flip

tOGGLE swaps the case of every letter. Lowercase letters go up, uppercase letters go down, and everything else stays put. It is the fastest fix for text typed with caps lock on: toggle it once and the words fall back into place, though the first letter of each sentence will need one more tap.

Some characters have no partner to swap with. ß has no single uppercase form, so a toggle leaves it as ß while its neighbours flip. The same applies to a few titlecase letters used in Croatian and Serbian, which have three forms rather than two.

Digits, punctuation and spaces are untouched, which makes toggle a quick way to test a font at small sizes.

Accents, ß, and the Turkish dotted i

Most accented letters convert cleanly. é becomes É, ñ becomes Ñ, ü becomes Ü, and the same holds for Greek and Cyrillic alphabets. The trouble starts where one character maps to two, or where a language has its own idea about what a letter is.

Unicode keeps these rules in a file called SpecialCasing.txt, which is part of the Unicode character database and is updated with each version of the standard. The file is why STRASSE has 7 characters while straße has 6, and why a length check written for English text can fail on German.

Turkish is the other trap. The capital I lowercases to a plain i in English, but to a dotless ı in Turkish. The lowercase i uppercases to I in English and to İ in Turkish. JavaScript offers toLocaleUpperCase for exactly this reason, and a converter that ignores the locale will mangle Turkish names. İstanbul has 8 characters and becomes 9 code points in lowercase, because the dot is stored as a separate mark.

CSS, Excel and JavaScript: three places case gets faked

Not every case change is real. Some tools change only what you see, and the text underneath keeps its original form. Knowing which is which saves a lot of confusion.

CSS is the one that catches people. The W3C CSS text module defines text-transform as a rendering step: the browser draws HELLO but the page still holds Hello. Copy that text into an email and you get Hello. A form field styled with text-transform: uppercase submits exactly what the user typed, lower case and all.

Excel is the opposite. UPPER, LOWER and PROPER return real text, but they return it in a new cell, so you have to copy the result and paste it back as values to replace the original. PROPER has two quirks worth knowing. It capitalizes the letter after an apostrophe, so don't becomes Don'T, and it capitalizes after a hyphen, so e-mail becomes E-Mail.

Case in search, passwords and file names

Case handling changes from one system to the next, and the difference matters more than most people expect.

Web search is case blind. A query for NASA and a query for nasa return the same results, which is why nobody bothers with capitals when they type. Passwords are the other extreme: they are case sensitive by design, so Password1 and password1 are two different keys.

The arithmetic explains why. Eight lowercase letters give 26 to the eighth power, which is 208,827,064,576 combinations. Allow both cases and the base doubles to 52, so the same 8 positions give 53,459,728,531,456 combinations. That is 256 times more work for a password cracker, and it costs the user nothing but a held shift key.

File names sit in between. Windows and macOS treat Report.PDF and report.pdf as the same file by default, while a Linux server treats them as two files that can sit side by side in one folder. Domain names ignore case, but the path after the domain can be case sensitive, so a link to /Images/Logo.png can break when the file is named logo.png.

Two quick conversions, both checked against the tables above. The phrase a guide to the best coffee shops in town is 40 characters and 9 words. Title Case returns A Guide to the Best Coffee Shops in Town, with 6 capitals and 3 small words left down. The German word straße is 6 characters, and UPPER returns STRASSE at 7, one more than the input.