What happens to numbers and punctuation?

Only alphabetic characters have a case to swap. Digits, spaces, symbols, and punctuation pass through completely unchanged so the structure of your text is preserved.

Is this the same as a case converter?

Not quite. A case converter forces everything to one case, such as ALL CAPS or all lowercase. This tool inverts each letter individually, so a mixed string keeps its mix but with every case flipped.

Does it handle accented letters?

Yes. Letters like é or Ñ have a defined upper and lower form, so they are toggled correctly. Characters that have no distinct case, such as symbols, are left alone.

Is my text uploaded anywhere?

No. All processing happens locally in your browser with JavaScript. Your text never leaves your device, which makes it safe for sensitive content.

Toggle Upper/Lowercase

Toggling case flips the capitalization of each letter independently: an uppercase A becomes a lowercase a, and a lowercase z becomes an uppercase Z. It is handy for fixing text typed with Caps Lock left on, or for quickly creating a “reversed case” effect.

How it works

The tool walks through your text one character at a time. For each character it compares the character to its own uppercase and lowercase forms:

lower = char.toLowerCase()
upper = char.toUpperCase()
if lower === upper      -> not a letter, keep as-is
else if char === lower  -> output the uppercase form
else                    -> output the lowercase form

Because the decision is per-character, mixed-case input keeps its pattern but with every case inverted. Non-letters fall into the first branch and are copied straight through.

Example and notes

The input Hello World becomes hELLO wORLD. A string like iPhone 12 Pro becomes Iphone 12 pRO. Numbers and the space stay exactly where they are. This is a reversible operation: toggling twice returns the original text.