🔤 Case Converter
A case converter for every case at once — sentence, title (AP and Chicago), camelCase, PascalCase, snake_case, kebab-case — updating as you type.
Every conversion updates as you type. Nothing is uploaded — this runs in your browser.
the quick brown fox jumps over the lazy dog
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
The quick brown fox jumps over the lazy dog
The Quick Brown Fox Jumps Over The Lazy Dog
The Quick Brown Fox Jumps over the Lazy Dog
The Quick Brown Fox Jumps Over the Lazy Dog
tHe QuIcK bRoWn FoX jUmPs OvEr ThE lAzY dOg
THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG
theQuickBrownFoxJumpsOverTheLazyDog
TheQuickBrownFoxJumpsOverTheLazyDog
the_quick_brown_fox_jumps_over_the_lazy_dog
THE_QUICK_BROWN_FOX_JUMPS_OVER_THE_LAZY_DOG
the-quick-brown-fox-jumps-over-the-lazy-dog
The-Quick-Brown-Fox-Jumps-Over-The-Lazy-Dog
the.quick.brown.fox.jumps.over.the.lazy.dog
What Case Converter Does
Changing case looks like a solved problem until you try to define "title case". Capitalizing every word is easy and is not what a publisher does — real title case leaves articles, conjunctions and short prepositions in lowercase, which is why the book is "The Lord of the Rings" and not "The Lord Of The Rings".
It gets more interesting than that, because the two dominant American style guides disagree with each other. Chicago keeps every preposition lowercase however long it is. Associated Press style capitalizes any word of four letters or more. So the same film is "Gone with the Wind" under Chicago and "Gone With the Wind" under AP, and both are correct. This tool produces both, which no other converter does.
The developer cases have their own rules and their own trap. Converting to camelCase means finding word boundaries, and a converter that lowercases the text first destroys the boundaries that were already there — "HelloWorld" collapses to "helloworld" instead of becoming "helloWorld". Getting that right means understanding camelCase input, acronyms like HTTPServer, digits and separators before doing anything.
Every conversion here updates as you type and runs in your browser, and each one is explained below so you can tell which you actually need.
How to Use Case Converter
- Paste or type your text in the box
- Every case is generated at once and updates as you type
- Compare the two Title Case options if you are writing to a style guide
- Press Copy next to whichever result you want
Formula Used by Case Converter
Title case, in rules
Capitalize everything except minor words — unless the minor word is first or last
- Minor words
- Articles (a, an, the), coordinating conjunctions (and, but, or, nor, for, so, yet) and prepositions
- The disagreement
- Chicago lowercases all prepositions; AP capitalizes those of four letters or more
Worked example
"gone with the wind"
- "gone" is first, so capitalize
- "with" is a 4-letter preposition — the guides differ
- "the" is an article, lowercase
- "wind" is last, capitalize
Result: Chicago: Gone with the Wind · AP: Gone With the Wind
Finding word boundaries
Split on separators, and also between a lowercase letter and an uppercase one
- lower→upper
- fooBar becomes foo | Bar
- Acronym rule
- A run of capitals followed by a capital-plus-lowercase splits: HTTPServer becomes HTTP | Server
Worked example
Converting "HTTPServerError" to snake_case
- Split on the acronym boundary: HTTP | ServerError
- Split lower→upper: HTTP | Server | Error
- Lowercase and join with underscores
Result: http_server_error — not the httpservererror a naive converter produces
Sentence case boundaries
Capitalize at the start, after . ? or !, and after each line break
- Why all three
- Breaking only on "." leaves questions and exclamations lowercase
Worked example
"hello. really? yes! ok"
- Lowercase everything
- Capitalize the first letter
- Capitalize after each of . ? !
Result: Hello. Really? Yes! Ok
Every conversion on one string
The input is "the quick brown fox". Note that Capitalized Case and the two Title Cases give three different answers to what sounds like one question.
| Case | Result | Where it is used |
|---|---|---|
| lower case | the quick brown fox | Normalizing input, tags |
| UPPER CASE | THE QUICK BROWN FOX | Headings, emphasis, constants |
| Sentence case | The quick brown fox | Body text, UI labels |
| Capitalized Case | The Quick Brown Fox | Names, some headings |
| Title Case (Chicago) | The Quick Brown Fox | Books, academic writing |
| Title Case (AP) | The Quick Brown Fox | Journalism, press releases |
| camelCase | theQuickBrownFox | JavaScript, Java, C# variables |
| PascalCase | TheQuickBrownFox | Class and component names |
| snake_case | the_quick_brown_fox | Python, Ruby, database columns |
| CONSTANT_CASE | THE_QUICK_BROWN_FOX | Constants, environment variables |
| kebab-case | the-quick-brown-fox | URLs, CSS classes, file names |
| Train-Case | The-Quick-Brown-Fox | HTTP headers |
| dot.case | the.quick.brown.fox | Config keys, namespaces |
Where AP and Chicago diverge
Only prepositions are in dispute. Articles and coordinating conjunctions stay lowercase in both, and a minor word that begins or ends the title is always capitalized.
| Word type | Chicago | AP | Example |
|---|---|---|---|
| Articles — a, an, the | lowercase | lowercase | A Tale of Two Cities |
| Conjunctions — and, but, or | lowercase | lowercase | The Sound and the Fury |
| Prepositions of 1–3 letters | lowercase | lowercase | Out of Africa |
| Prepositions of 4+ letters | lowercase | Capitalized | Gone with / With the Wind |
| Any minor word, first or last | Capitalized | Capitalized | Nothing to Look At |
| Existing acronyms | left alone | left alone | The NASA Report |
Which case for which job
These are conventions, not preferences — code review comments about them are about consistency with the surrounding language.
| Context | Convention | Why |
|---|---|---|
| URL slug | kebab-case | Search engines read hyphens as word separators, underscores as joiners |
| CSS class | kebab-case | Matches CSS property naming |
| Python / Ruby variable | snake_case | Language style guides (PEP 8) |
| JavaScript variable | camelCase | Language convention |
| Class or React component | PascalCase | Distinguishes types from values |
| Environment variable | CONSTANT_CASE | Long-standing shell convention |
| HTTP header | Train-Case | Content-Type, X-Request-Id |
How to Read Your Result
Capitalized Case and Title Case are not synonyms
This is the distinction most converters blur and the one that matters if anything you write will be edited. Capitalizing every word is a mechanical operation; title case is an editorial one that depends on each word's part of speech. "The Lord Of The Rings" is not a stylistic variant of the correct form, it is simply wrong in every major style guide. If you are writing headlines, book titles, or anything that goes past an editor, you want title case.
The same word can be a preposition or not
Rule-based title casing has a real limit: parts of speech are contextual. "Up" is a preposition in "Look up the Answer" and part of a phrasal verb in "Turn Up the Volume", where most guides capitalize it. No word list can tell those apart, so any automatic title caser — including this one — will occasionally lowercase a word that should be capitalized. Treat the output as a strong first pass on anything being published.
Hyphens and underscores are not interchangeable in URLs
Google has been explicit about this for years: hyphens separate words in a URL, underscores join them. So /blue-widgets is read as two words and can rank for "blue widgets", while /blue_widgets is read as the single token "blue_widgets". For anything that appears in a URL, kebab-case is the right answer and it is not merely a style preference. The same reasoning does not apply to code, where underscores are simply a language convention.
Case conversion is not always reversible
Uppercasing loses information you cannot recover: "US" and "us" both become "US", and lowercasing them both gives "us". Acronyms are the usual casualty — run a sentence containing NASA or HTML through lower case and no converter can put the capitals back, because the knowledge of which words were acronyms is gone. Keep the original if you might need it, and prefer conversions that preserve rather than flatten, which is why this tool leaves existing all-caps acronyms alone in title case.
Casing is language-dependent
Turkish has a dotted and a dotless i, and lowercasing "I" correctly gives "ı" in Turkish and "i" in English. German ß uppercases to SS. Many scripts — Chinese, Japanese, Arabic, Hebrew, Devanagari — have no case at all, so a case conversion leaves them untouched. This tool uses locale-aware casing rather than the naive ASCII kind, and preserves non-ASCII characters through the separator-based conversions rather than stripping them.
Why every conversion is shown at once
The competing tools make you pick a conversion and press a button, which means comparing two options requires two clicks and a mental note. Showing all of them live makes the comparison the default — and the comparison is the useful part, because the question people actually have is usually "which of these is the one I want" rather than "apply this specific transformation".
Limitations & Accuracy Notes
- Title case is rule-based and cannot resolve parts of speech from context. Phrasal verbs like "Turn Up the Volume" may be lowercased where a style guide would capitalize them.
- Only AP and Chicago conventions are offered. MLA, APA and house styles differ in details — APA, for instance, capitalizes all words of four or more letters including conjunctions.
- Sentence case detects boundaries at . ? ! and line breaks. Abbreviations containing a period, such as "Dr." or "e.g.", will trigger a capital on the following word.
- The developer cases discard the original separators by design. Converting to snake_case and back to the original punctuation is not possible.
- Casing follows your browser's locale rules. Text in a language your browser is not set to may cast edge-case letters differently — the Turkish dotless i being the classic example.
- Scripts without case, including Chinese, Japanese, Arabic and Hebrew, are unchanged by the case conversions, which is correct rather than a failure.
Frequently Asked Questions
What is the difference between Title Case and Capitalized Case?
Why do AP and Chicago title case differ?
Which case should I use for a URL slug?
When would I use snake_case rather than camelCase?
Will this handle accents and non-English text?
Is my text sent anywhere?
References & Further Reading
- Unicode Character Database — SpecialCasing.txt — The data file defining the language-specific case mappings quoted above, including the Turkish and Azeri rules for the dotted and dotless i and the German ß
- Google Search Central — URL structure best practices — Google's guidance that hyphens separate words in URLs while underscores join them, which is why kebab-case is the slug convention
- Convert Case — The #1 result for this term, and the source of the Title Case versus Capitalized Case distinction adopted here
- PEP 8 — Style Guide for Python Code, naming conventions — The reference for snake_case variables and PascalCase class names cited in the conventions table