Types of Letter Case
Letter case is the difference between capital letters (uppercase) and small letters (lowercase). A case style is a rule for which letters in a piece of text are capitals. Writers switch styles to match a style guide, a platform, or a convention, and a case converter applies the rule to text you paste instead of retyping it.
Some styles treat every letter the same way: uppercase makes every letter a capital, and lowercase makes every letter small. Others depend on words and sentences. Sentence case capitalizes the first word of each sentence, and title case capitalizes the major words of a title while short words stay lowercase.
Case styles
Each of these converters applies one style to the whole text. Uppercase, lowercase, alternating case, and small caps change letters one by one; sentence case, title case, proper case, and capitalize first letter decide by word or sentence.
Uppercase
Uppercase, also called all caps, is text in which every letter is a capital letter. This uppercase converter changes each lowercase letter to its capital form, accented letters included, and leaves numbers, punctuation, spacing, and line breaks exactly as you typed them, so lists and paragraphs keep their layout.
Example: breaking news: council approves budget becomes BREAKING NEWS: COUNCIL APPROVES BUDGET
Uppercase ConverterLowercase
Lowercase is text written entirely in small letters, with no capitals. This lowercase converter changes each capital letter to its small form, in any alphabet that has letter case, and leaves numbers, punctuation, spacing, and line breaks as they were. Acronyms and names lose their capitals too, so check them afterward.
Example: BREAKING NEWS: COUNCIL APPROVES BUDGET becomes breaking news: council approves budget
Lowercase ConverterTitle case
Title case is a capitalization style for titles and headlines in which the major words start with a capital letter and short articles, conjunctions, and prepositions stay lowercase. This title case converter follows the AP Stylebook rules, keeps acronyms such as NASA, and treats each line as a separate title.
Example: the quick brown fox jumps over the lazy dog becomes The Quick Brown Fox Jumps Over the Lazy Dog
Title Case ConverterSentence case
Sentence case is the capitalization of ordinary prose: the first word of each sentence starts with a capital letter and the other words are lowercase. This sentence case converter finds sentence boundaries, skips decimals and abbreviations such as Dr., and keeps acronyms (NASA) and mixed-case words (iPhone) when the rest of the line is not in capitals.
Example: THE QUICK BROWN FOX. IT JUMPS. becomes The quick brown fox. It jumps.
Sentence Case ConverterProper case
Proper case capitalizes the first letter of every word, the way names and places are written. This proper case converter capitalizes each word and each part of a hyphenated word, spells names such as O'Brien and McDonald, and never lowercases a letter, so short words such as "of" and "the" are capitalized too.
Example: john smith becomes John Smith
Proper Case ConverterFirst-letter capitalization
First-letter capitalization gives a piece of text a single capital at its very start. This tool capitalizes the first character of your text and lowercases everything after it, acronyms and later sentences included, which suits short labels, list items, and single phrases rather than paragraphs of several sentences.
Example: hello world becomes Hello world
Capitalize First LetterSmall caps
Small caps are capital letters drawn at about the height of lowercase letters. This small caps converter replaces lowercase letters from a to z, except q and x, with Unicode small capital characters, so the look survives pasting into places where you cannot change the font, such as social media bios. Capital letters, numbers, and punctuation stay as typed.
Example: hello world becomes ʜᴇʟʟᴏ ᴡᴏʀʟᴅ
Small Caps ConverterAlternating case
Alternating case switches between capital and lowercase letters one letter at a time, often used online to signal a mocking or sarcastic tone. This alternating case converter starts with a capital, counts only letters, and carries the pattern across words and lines, so spaces, numbers, and punctuation never break it.
Example: hello world becomes HeLlO wOrLd
Alternating Case ConverterAll tools in this category: Case Conversion
Title case by style guide
Style guides agree that titles capitalize their major words, but they differ on short words such as articles, prepositions, and conjunctions, and on the last word of a title. These are the four styles the converters follow.
AP style title case
AP style title case is the capitalization the AP Stylebook prescribes for titles of works such as books, movies, and songs. Principal words and every word of four or more letters are capitalized, and articles and short conjunctions and prepositions stay lowercase unless they come first or last. This converter applies those rules line by line.
Example: the man with the golden gun becomes The Man With the Golden Gun
AP Style Title Case ConverterChicago style title case
Chicago style title case is the headline-style capitalization in The Chicago Manual of Style. The 18th edition (2024) capitalizes major words and prepositions of five or more letters, and lowercases articles, shorter prepositions, and the conjunctions and, but, for, or, and nor. This converter applies those rules to each line you type.
Example: the man with the golden gun becomes The Man with the Golden Gun
Chicago Style Title Case ConverterMLA style title case
MLA style title case is the capitalization the MLA Handbook, 9th edition, uses for titles of works. The first word, the last word, and principal words are capitalized, while articles, prepositions of any length, coordinating conjunctions, and the "to" of infinitives stay lowercase. This converter applies those rules to each line of your text.
Example: the calm before the storm becomes The Calm before the Storm
MLA Style Title Case ConverterAPA style title case
APA style title case is the capitalization the Publication Manual of the American Psychological Association, 7th edition, uses for paper titles and headings. Major words and every word of four or more letters are capitalized, and only minor words of three letters or fewer stay lowercase. This converter applies those rules to each line.
Example: the man with the golden gun becomes The Man With the Golden Gun
APA Style Title Case ConverterAll tools in this category: Title Capitalization
The edition, rules, limits, and test cases for each style: Title Case Rules by Style Guide
Programming naming cases
Code names cannot contain spaces, so programming cases mark where one word ends and the next begins: with a capital letter (camelCase, PascalCase), or with an underscore, hyphen, or period (snake_case, kebab-case, CONSTANT_CASE, dot.case). Each language and format has its own convention.
camelCase
camelCase writes a name as one word: the first word is lowercase and every word after it starts with a capital letter, as in userAccountId. This converter turns plain words or names in another case into camelCase, splitting acronyms and dropping punctuation, with one name per line of input.
Example: user account id becomes userAccountId
camelCase ConverterPascalCase
PascalCase, also called upper camel case, writes a name as one word in which every word starts with a capital letter, as in UserProfileCard. This converter turns plain words or names in another case into PascalCase, splitting acronyms and dropping punctuation, with one name per line of input.
Example: user profile card becomes UserProfileCard
PascalCase Convertersnake_case
snake_case writes a name in lowercase letters with an underscore between words, as in user_account_id. This converter turns plain words or names in another case, such as camelCase or kebab-case, into snake_case, splitting acronyms and dropping punctuation, with one name per line of input.
Example: userAccountId becomes user_account_id
snake_case Converterkebab-case
kebab-case writes a name in lowercase letters with a hyphen between words, as in main-navigation-menu. This converter turns plain words or names in another case, such as camelCase or snake_case, into kebab-case, splitting acronyms and dropping punctuation, with one name per line of input.
Example: Main Navigation Menu becomes main-navigation-menu
kebab-case ConverterCONSTANT_CASE
CONSTANT_CASE, also called screaming snake case, writes a name in capital letters with an underscore between words, as in MAX_RETRY_COUNT. This converter turns plain words or names in another case into CONSTANT_CASE, splitting acronyms and dropping punctuation, with one name per line of input.
Example: max retry count becomes MAX_RETRY_COUNT
CONSTANT_CASE Converterdot.case
dot.case writes a name in lowercase letters with a period between words, as in server.port. This converter turns plain words or names in another case, such as camelCase or CONSTANT_CASE, into dot.case, splitting acronyms and dropping other punctuation, with one name per line of input.
Example: server port becomes server.port
dot.case ConverterAll tools in this category: Programming Case
How the two most common conventions differ, with examples: camelCase vs snake_case
Which case to use
| What you are writing | Case style |
|---|---|
| Ordinary sentences and paragraphs | Sentence case |
| Headlines and titles of books, articles, and other works | Title case |
| A paper title or headings in APA style | APA style title case |
| Article and book titles in an APA 7 reference list | Sentence case |
| Titles in an essay or works-cited list in MLA style | MLA style title case |
| Book, chapter, and section titles that follow Chicago style | Chicago style title case |
| Titles of works mentioned in a news story in AP style | AP style title case |
| Names, places, and labels typed in lowercase | Proper case |
| Short labels and notices your house style sets in all caps | Uppercase |
| Email addresses, tags, and URL slugs before you compare or store them | Lowercase |
| Variable and function names in JavaScript, TypeScript, and Java | camelCase |
| Function and variable names in Python, Ruby, and Rust | snake_case |
Case styles compared
What a case converter does
A case converter rewrites the capitalization of text by rule. Uppercase and lowercase change every letter the same way. Title case and sentence case need rules about words: which words count as minor, where each sentence starts, and what to do with acronyms.
The converters on this site work from word lists and punctuation. They do not detect parts of speech or recognize proper nouns, so a word such as "up" is treated the same way whether it is a preposition or an adverb, and a name typed in lowercase is not capitalized by sentence case. Read the result before you publish it, especially names that use unusual capitalization.