Case Converter — Upper, Lower, Title Case

Changing text case

Paste text and convert it between upper case, lower case, sentence case, title case and the programming conventions. It is a small job that is tedious by hand and easy to get subtly wrong, particularly title case, which follows rules most people apply inconsistently.

The conversions

Style	Example	Used for
UPPER CASE	THE QUICK BROWN FOX	Headings, acronyms, emphasis
lower case	the quick brown fox	Normalising input, tags, URLs
Sentence case	The quick brown fox	Body text, UI labels
Title Case	The Quick Brown Fox	Headlines, book and article titles
camelCase	theQuickBrownFox	Variables in Java, JavaScript
PascalCase	TheQuickBrownFox	Class names, React components
snake_case	the_quick_brown_fox	Python, Ruby, database columns
kebab-case	the-quick-brown-fox	URLs, CSS classes, filenames

Title case is not just capitalising everything

The convention most style guides follow capitalises the first and last words, plus all major words, but leaves short function words lowercase in the middle of a title:

Capitalise: nouns, pronouns, verbs, adjectives, adverbs, and subordinating conjunctions such as because and although.
Leave lowercase: articles (a, an, the), coordinating conjunctions (and, but, or, nor, for, so, yet), and short prepositions (in, on, at, to, of, by, up) — unless they begin or end the title.

So it is The Sound and the Fury, not The Sound And The Fury. Style guides disagree at the margins: Chicago lowercases all prepositions regardless of length, while AP capitalises those of four letters or more, making it Gone With the Wind in one and Gone With The Wind in neither. Verbs are capitalised however short they are, which is why Is and Be take capitals in a headline.

Sentence case is winning

Most modern interface style guides — including Google's and Apple's — now specify sentence case for headings, buttons and labels. The reasoning is that it reads faster, handles product names and acronyms more gracefully, and translates into other languages without the awkwardness that title case creates in German or French, where capitalisation rules differ entirely. If you are writing UI text and have no house style, sentence case is the safer default.

Programming conventions

Case style in code is not decoration; it carries meaning that readers rely on.

camelCase — variables and functions in JavaScript, Java, C# methods.
PascalCase — classes, types and React components. The capital signals "this is a type, not a value".
snake_case — variables and functions in Python, Ruby and Rust, and SQL column names.
SCREAMING_SNAKE_CASE — constants and environment variables across most languages.
kebab-case — URLs, CSS class names, HTML attributes and command-line flags. Not valid in most identifiers because the hyphen reads as a minus sign.

For URLs specifically, hyphens are preferable to underscores. Search engines treat a hyphen as a word separator and an underscore as a word joiner, so blue-widgets is read as two words and blue_widgets as one.

Case and non-English text

Case conversion is not universal. Chinese, Japanese, Korean, Arabic, Hebrew and several Indic scripts have no concept of case at all, so conversion leaves them unchanged. Where case does exist, it can behave unexpectedly:

The German sharp s uppercases to SS, so a five-letter word can become six letters — meaning uppercasing is not always reversible.
Turkish has dotted and dotless i as distinct letters, so lowercasing "I" gives a different result in Turkish locale than in English. This has caused real bugs in software that uppercases identifiers before comparing them.
Greek final sigma differs from medial sigma, so lowercasing a Greek word requires knowing where the word ends.

This tool applies standard Unicode case mapping, which handles most of this correctly but uses the default locale rather than a language-specific one.

Everything runs locally

The conversion happens in your browser. Nothing you paste is uploaded, which matters if you are reformatting anything confidential. Long documents convert instantly since it is a straightforward character mapping.

Frequently asked questions

What is the difference between title case and capitalising every word?

Title case leaves articles, coordinating conjunctions and short prepositions lowercase in the middle of a title, so it is "The Sound and the Fury". Capitalising every word would give "The Sound And The Fury", which no major style guide accepts.

Should headings use title case or sentence case?

Sentence case is the modern default for interfaces and increasingly for web content — both Google and Apple specify it. Title case remains standard for book titles, article headlines and academic references. If you have a house style, follow it.

What is the difference between camelCase and PascalCase?

Only the first letter. camelCase starts lowercase and is used for variables and functions; PascalCase starts uppercase and is used for classes, types and components. The distinction lets a reader tell a type from a value at a glance.

Should URLs use hyphens or underscores?

Hyphens. Search engines treat a hyphen as a word separator and an underscore as a joiner, so "annual-report" is read as two words while "annual_report" is read as one. Hyphens are also easier to read in a long slug.

Does this work with accented and non-Latin text?

Yes, using standard Unicode case mapping, so accented Latin, Greek and Cyrillic convert correctly. Scripts without case — Chinese, Japanese, Arabic, Hebrew, Devanagari — pass through unchanged.