Choose Escape or Unescape, paste your text, then click Convert. Escape turns accented letters, CJK and emoji into \uXXXX sequences; Unescape reverses them.
ASCII-only source avoids encoding problems in older toolchains, minifiers or systems that mangle UTF-8. Escaping keeps the exact characters while making the file pure ASCII.
Yes. Characters above U+FFFF are emitted as UTF-16 surrogate pairs (two \uXXXX units) on escape, and decoding also understands the \u{...} code-point form.
No. Printable ASCII (space through ~) is left as-is. Only non-ASCII and control characters are converted, so your code stays readable.