🔡 Case Converter: Change Text to Uppercase, Lowercase and More

What is the Case Converter?

Letter case is the difference between capital letters (A, B, C) and small letters (a, b, c). Most writing mixes the two by convention: a sentence starts with a capital, proper nouns are capitalised, and the rest is lowercase. A case converter automates the tedious job of changing that convention across a whole block of text, which is far faster and more reliable than retyping or holding Shift while you fix each word by hand. Whether you are cleaning up a headline that arrived in ALL CAPS or building a tidy variable name from a label, the right case style takes one click instead of dozens of keystrokes.

The styles fall into two broad groups. Reading styles are meant for human text: UPPERCASE shouts and works for short acronyms or legal notices, lowercase is quiet and informal, Title Case suits headings and headlines, and Sentence case is the normal flow of prose with only the first word and proper nouns capitalised. Programmer styles join words together without spaces because most languages do not allow spaces in identifiers: camelCase (firstNameField), snake_case (first_name_field), and kebab-case (first-name-field) are the three you meet most often in code, file names, URLs, and database columns. A good case converter handles both groups so a writer and a developer can use the same tool.

Under the hood, converting between these styles means deciding where one word ends and the next begins. For spaced text that is easy. For programmer styles the converter also has to split existing camelCase boundaries (the capital M in fileName marks a new word) and treat punctuation, spaces, hyphens, and underscores as separators. Once the words are identified, each style simply rejoins them with its own rule: a separator character for snake and kebab, capitalised first letters with no gaps for camel and Pascal, or a single leading capital for Sentence case. This tokenise-then-rejoin approach is why a clean case converter can round-trip text between any two styles without losing the word boundaries.

Title Case deserves a special note because it is the style most people get wrong. Publishers follow style guides such as AP, Chicago, MLA, and APA, and these guides disagree on the small words. The shared rule is that the first and last words are always capitalised, along with all major words: nouns, pronouns, verbs, adjectives, and adverbs. The disagreement is about articles, conjunctions, and prepositions. AP style capitalises any word of four letters or more, so it writes With and From with capitals. Chicago and MLA lowercase prepositions regardless of length and lowercase the articles a, an, and the. A simple case converter capitalises the first letter of every word, which is fast and consistent but not always strictly correct, so proofread headlines if your publication enforces a specific guide.

Beyond the seven core styles, the wider family of text case transforms includes PascalCase (every word capitalised with no spaces, used for class names), CONSTANT_CASE or screaming snake case (uppercase words joined by underscores, used for constants and environment variables), dot.case for nested keys, Train-Case for some HTTP headers, plus playful options like aLtErNaTiNg case and tOGGLE case that flip each letter. Knowing which transform a given context expects saves real debugging time: a JSON key in the wrong case, a CSS class that should be kebab-case, or an environment variable that should be CONSTANT_CASE will silently fail rather than throw an obvious error.

Because this case converter runs entirely in your browser with plain JavaScript, there is no upload, no account, and no limit on how often you convert. That makes it safe for confidential drafts, internal documentation, and code you cannot paste into a remote service. Use it to standardise a spreadsheet column, normalise messy data exported from a PDF, generate consistent file names, or simply rescue a heading that someone typed with Caps Lock on.

When to use it

• Fixing a heading or title that was typed in all caps or all lowercase so it reads as proper Title Case.
• Turning a label like "First Name" into a code-friendly variable such as firstName, first_name, or first-name.
• Cleaning up text pasted from a spreadsheet or PDF where the capitalisation came out wrong.
• Creating a URL slug or file name from a page title by converting it to kebab-case.
• Normalising a column of names or product titles so every row uses the same capitalisation before importing it.
• Converting a database column name between snake_case and camelCase when moving data between a backend and a frontend.

How to use the Case Converter

1. Type or paste your text into the input box.
2. Click the case you want: UPPERCASE, lowercase, Title Case, Sentence case, camelCase, snake_case, or kebab-case.
3. Read the converted text in the result box below.
4. Click Copy to send the result to your clipboard, then paste it wherever you need it.
5. Need a different style? Click another button on the same text, or clear the box and paste fresh text.

Formula & method

Worked examples

How each case style rewrites the phrase "Hello World Example"

Programmer case styles and where each one belongs

Title case: which small words to capitalise by style guide

Common mistakes to avoid

• Confusing Title Case with capitalising every letter. Title Case capitalises only the first letter of each word (Hello World). Putting every letter in capitals is UPPERCASE (HELLO WORLD), which reads as shouting and is harder to scan.
• Expecting Title Case to skip small words automatically. Strict editorial title case leaves short words like "and", "of", or "the" lowercase, but the exact list differs between AP, Chicago, and MLA. This tool capitalises the first letter of every word, so always proofread a headline if you follow a specific style guide.
• Using spaces in code names. Programming languages do not allow spaces inside variable or file names. That is the whole reason camelCase, snake_case, and kebab-case exist, so pick one of those rather than leaving spaces in.
• Mixing snake_case and kebab-case in code. Underscores and hyphens are not interchangeable. Many languages treat a hyphen as a minus sign, so kebab-case is usually safe only in URLs, CSS, and file names, not in variable names.
• Forgetting that UPPERCASE destroys original casing. Converting to UPPERCASE or lowercase is one-way: once "iPhone" becomes "IPHONE" or "iphone", the tool cannot guess the original mixed case back. Keep a copy of the source text if you might need it.
• Capitalising acronyms as words in Title Case. A simple Title Case pass turns "NASA report" into "Nasa Report". For text with acronyms, convert first and then fix the acronyms by hand, since the tool treats every word the same way.

Glossary

Letter case

Whether a letter is written as a capital (uppercase) or small (lowercase) form, such as A versus a.

Title Case

A style where the first letter of each word is capitalised, commonly used for headings and titles.

Sentence case

Normal prose capitalisation: only the first word of a sentence and proper nouns start with a capital letter.

camelCase

A naming style where words are joined with no spaces, the first word is lowercase, and each later word starts with a capital, like firstName.

PascalCase

Like camelCase but the first word is also capitalised, like FirstName. Often used for class and type names.

snake_case

A naming style where lowercase words are joined by underscores, like first_name.

kebab-case

A naming style where lowercase words are joined by hyphens, like first-name, common in URLs and CSS.

CONSTANT_CASE

Uppercase words joined by underscores, like MAX_RETRIES. Also called screaming snake case and used for constants and environment variables.

Frequently asked questions