Case Converter
Text & Dev ToolsSentence, title, upper and lower case, and the code styles — with the title-case rule stated.
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Result
The Lord of the Rings: The Fellowship of the Ring
Short words — a, an, the, and, but, or, nor, for, so, yet, and prepositions of three letters or fewer — stay lower-case unless they start or end the title or follow a colon. Words already written with a capital inside, such as iPhone or NASA, are left alone.
How this is calculated
Sentence case lower-case all, capitalise the first letter of each sentence
Title Case capitalise each word, except a · an · the · and · but · or · nor
· for · so · yet · as · at · by · in · of · off · on · per · to
· up · via · vs — unless first, last, or after a colon
camelCase helloWorld PascalCase HelloWorld
snake_case hello_world kebab-case hello-world
CONSTANT_CASE HELLO_WORLDHow it works
Upper and lower case are the simple ones: every letter changes, including accented letters and letters from other alphabets. A few characters change length as they do — the German ß becomes SS in capitals — which is the language's rule rather than a quirk of this tool.
Title case has no single correct answer. The major style guides disagree about which short words stay lower-case: AP and APA capitalise prepositions of four letters or more, while the Chicago Manual of Style, in its own answer based on the 17th edition, lower-cases all prepositions regardless of length. This converter uses one plain rule and states it: articles, coordinating conjunctions and prepositions of three letters or fewer stay lower-case, unless they are the first or last word or follow a colon. So "what the internet is for" becomes "What the Internet Is For" — "is" is a verb and "for" ends the title. Check the house style you are writing for before relying on it.
Words that already have a capital after their first letter — iPhone, McDonald's, NASA — are left exactly as they were, because lower-casing them is almost always a mistake. Sentence case cannot tell a name from an ordinary word, though, so it lower-cases everything except the start of each sentence, and names need their capitals put back by hand.
The code styles split text into words first, at spaces, punctuation and changes of case, so they also convert between each other: getUserIDFromURL becomes get_user_id_from_url, and MAX_RETRY_COUNT becomes maxRetryCount. A run of capitals is kept together as one word, which is what keeps XML in parseXMLHttpRequest from splitting into three letters.
Worked example
One title, and one variable name, converted
- the lord of the rings: the fellowship of the ring
- → The Lord of the Rings: The Fellowship of the Ring
- "of" and "the" stay small; "The" after the colon is capitalised
- getUserIDFromURL
- → words: get · User · ID · From · URL
- → snake_case get_user_id_from_url
- → CONSTANT_CASE GET_USER_ID_FROM_URL
Titles follow a stated rule; identifiers keep their word boundaries
How to use it
- Type or paste your text.
- Choose the case to convert to. The result updates straight away.
- For title case, read the rule under the result and check it against the style guide you are following.
- Copy the result.
What this tool does not do
- Title case follows one stated rule, not AP, Chicago or APA exactly. Those guides disagree with each other about prepositions and some conjunctions.
- Sentence case cannot recognise names, places or acronyms. It lower-cases them, so put their capitals back by hand.
- Letters change case by Unicode's general rules, not a particular language's. In Turkish and Azerbaijani, the dotted and dotless i do not convert the way those languages require.
- Sentences are detected by a full stop, question mark or exclamation mark followed by a space, so abbreviations such as "e.g. this" start a new sentence.
- Identifier styles keep only letters and digits; punctuation in the input is dropped.
Frequently asked questions
Which words stay lower-case in title case?
Here: a, an, the; and, but, or, nor, for, so, yet; and the prepositions as, at, by, in, of, off, on, per, to, up, via and vs — unless one of them is the first or last word, or comes straight after a colon. Longer prepositions such as from, with and without are capitalised. Style guides differ on exactly this point, so check the one you are writing for.
What is the difference between title case and sentence case?
Title case capitalises most words: "The Lord of the Rings". Sentence case capitalises only the first word and any proper nouns, the way an ordinary sentence is written: "The lord of the rings". Many publications now use sentence case for headlines because it is easier to read.
What is the difference between camelCase and PascalCase?
Only the first letter. camelCase starts lower-case — helloWorld — and is the common style for variables and functions in JavaScript and Java. PascalCase starts upper-case — HelloWorld — and is usual for class and type names.
When is snake_case used instead of kebab-case?
snake_case is common for variables and database columns in Python, Ruby and SQL. kebab-case uses hyphens, which most programming languages read as minus signs, so it appears where names are not code: URLs, CSS classes and file names. CONSTANT_CASE is snake_case in capitals, used for constants and environment variables.
Why did my acronym stay in capitals?
In title case, any word with a capital after its first letter is left untouched, so NASA and iPhone are not changed. In the code styles, a run of capitals is treated as one word — so URL becomes url in snake_case rather than u_r_l.
Is my text sent anywhere?
No. The conversion runs in your browser and no network request carries what you type. The only requests the page makes once you use it are small ones recording that the tool was used.
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Last updated 13 September 2026.