Text Case Converter

The five cases and what each one is for

• UPPERCASE — shouts. Historically used in telegrams (which had no lower case) and on road signs. Today, it's mostly for emphasis, acronyms, and legal disclaimers. Don't use it for body text: capitals are ~13% harder to read and screen readers will sometimes spell them out letter‑by‑letter.
• lowercase — quiet, conversational. Useful for code identifiers, URLs, and fixing accidentally caps‑locked paragraphs.
• Title Case — capitalises the first letter of every word. Good for headings and filenames. Note: strict editorial style guides (Chicago, AP) don't capitalise short words like of, the, and, a, in in the middle of a title. This tool uses the simpler "every word" rule, which is what most blog and social posts use; adjust manually if you're writing for a publication that cares.
• Sentence case — capitalises the first letter of each sentence and leaves the rest lowercase. The natural case for body copy. If you accidentally type a long message with caps lock on, this is the fix.
• aLtErNaTiNg CaSe — meme case, used to mock a quoted statement ("I'm telling mom"). A cultural artefact of late‑2010s internet; has no typographic utility beyond humour.

Why case changes are harder than they look

For ASCII English, case changes are trivial — every letter has a clean counterpart. For Unicode it gets interesting fast. German ß (eszett) uppercases to SS (two letters!). Turkish has a dotted İ and a dotless ı that don't round‑trip through generic toLowerCase(). Greek final sigma ς becomes non‑final σ when uppercased. This tool uses JavaScript's built‑in toLowerCase() / toUpperCase(), which handle most of these cases correctly via the Unicode default case mapping tables — but if you're working with professional Turkish or Azeri text you should double‑check the output.

Common uses

• Normalising an email list (convert all to lowercase before deduplication).
• Fixing a paper draft where someone typed an entire paragraph in caps.
• Generating consistent heading formatting for a blog.
• Converting database column values when migrating systems.
• Producing title strings for social media posts.

Privacy

The text you paste is transformed by a few lines of JavaScript running in your tab. There's no network call, no log, no upload. A good fit if what you're converting happens to be sensitive — contract clauses, passwords, names — because none of it leaves your machine.