Case Converter

The five case conversions: title case and sentence case are not the same

What each of the five modes does

The difference between the third and fifth rows is the easiest to confuse: "first letter" moves only one character (the one at the very start), whereas "sentence case" splits sentences at punctuation, uppercases the first letter of each sentence, and lowers unnecessary uppercase inside.

When to use which

• First letter: when you want to turn a sentence into a label, a title prefix, or button text. The user typed all lowercase and you only want the first character changed on display — here "title case" would break existing abbreviations (HTTP would become Http, and the fault is in the word-boundary rule, not the mode itself).
• Title case: title-style writing, organizing person and place names, and item names in a UI. Note that it also uppercases articles and prepositions (a, the, of), which violates the English title convention of "small words lowercase". Review the generated title once more by hand.
• Sentence case: fixes the readability of all-upper or all-lower input. Good for text exported from a database or a legacy system.
• UPPERCASE: constant names, warning text, and short labels that need visual emphasis. Note that long all-upper text significantly reduces readability (you lose the word-shape outline); a whole paragraph in uppercase is generally read as "shouting".
• lowercase: URL slugs, emails, and identifiers that need normalized comparison.

How the word boundary is decided

"Title case" depends on the word-boundary rule. The common implementation starts a new word after any non-alphanumeric character (space, hyphen, underscore, punctuation). This leads to a few real outcomes:

• A hyphenated word is uppercased: state-of-the-art becomes State-Of-The-Art.
• A letter after an apostrophe may be uppercased: don't may become Don'T, depending on whether the implementation treats the apostrophe as a boundary.
• The digit-letter boundary: words like 3d or v2 have no standard answer for how to split.

So automatically converted results always need a manual pass. They suit batch-drafting large amounts of text, not final output.

Where case conversion does not apply

• Language-specific rules. In Turkish, i uppercases to İ (dotted), not I; in German, a noun's initial capital is a grammar requirement. A generic conversion function follows Unicode defaults and does not handle these language exceptions.
• Content that should not change. Conversion processes the whole string and will alter code snippets, file paths, and URLs along with the prose. Text containing technical identifiers should not be case-converted wholesale — which is exactly why the naming-style converter below exists.
• Scenarios that only need case-insensitive comparison. If the goal is "ignore case to decide whether two texts are equal", the correct approach is to normalize case at comparison time, not to modify and save the original text — the latter causes irreversible data loss.

The tool runs the conversion locally in your browser; the text never reaches a server.