Case Converter

Case conversion method and review notes

The converter changes letter casing; it does not rewrite grammar or decide which words are proper nouns. Punctuation, digits, line breaks, and the order of characters remain in place. Uppercase and lowercase modes apply the browser’s Unicode-aware casing functions. Sentence and title modes first identify word boundaries, then apply a documented capitalization rule.

Methodology

1. UPPERCASE and lowercase use JavaScript string casing on the complete input, so alphabetic characters can change while punctuation and spacing are retained.
2. Sentence case lowers the working string, then capitalizes the first letter after the beginning of the text or sentence-ending punctuation. This is a mechanical rule, not a grammar parser.
3. Title case capitalizes detected words but keeps a short list of common articles, conjunctions, and prepositions lowercase when they are not the first or last word.
4. Alternating case changes successive letters only. Spaces and punctuation do not advance the upper/lower sequence.

Worked review example

Input “an API guide: using JSON in iOS” demonstrates the main limitation. A mechanical title-case result may change API, JSON, or iOS incorrectly because those spellings depend on domain knowledge. Use the output as a draft, then restore brands, acronyms, surnames, and style-guide exceptions. For a safer check, compare a short sample in every mode before processing a long document.

Test coverage and expected behavior

Test coverage includes empty input, multiline text, apostrophes, hyphenated words, accented Latin letters, emoji, and mixed acronym examples. Additional checks include that punctuation and line breaks survive a round trip through upper- and lowercase modes. The page does not claim locale-specific linguistic accuracy.

Decision checklist before using the output

Choose the target style from the document that will receive the text, not from personal preference. For a publication, identify its named style guide and keep a short exception list for brands, products, people, geographic names, abbreviations, and technical identifiers. Convert one representative heading and one difficult sentence first. Compare those samples with an approved document before changing the full source. After conversion, search for words that were originally mixed case, all caps, or intentionally lowercase. Pay special attention to iPhone-style brands, API names, surnames with particles, hyphenated compounds, and text inside code. If the source contains IDs, passwords, case-sensitive URLs, filenames, or program symbols, isolate them before conversion. The tool is appropriate for drafting display text; it is not appropriate for changing case-sensitive data in bulk without a backup and a domain-specific validation step.

Important limitations

• Turkish dotted and dotless I, Greek sigma, and other locale-sensitive casing can differ from an English editorial expectation.
• Title-case rules vary among AP, Chicago, APA, MLA, and house styles.
• The tool cannot identify names, trademarks, chemical symbols, or intentionally styled words.
• Changing case can alter string length for a small number of Unicode characters, so do not use character offsets from the original after conversion.

Sources and specifications

These references define the relevant format or browser behavior. They do not endorse WordCaseFix.

• Unicode casing specification
• ECMAScript String case conversion

Last reviewed: August 6, 2026