Toggle each letter between upper and lower case, leaving everything that is not a letter exactly as it was.
Hello World 123!
hELLO wORLD 123!
The result is the same for plain letters. Toggle Case checks explicitly that a character is a letter before touching it.
No. This tool runs entirely in your browser — nothing you type or paste is uploaded, logged or stored anywhere.
There is no fixed limit. Very large documents depend on your device’s memory, but ordinary pages and files are handled instantly.