Choose Encode or Decode, pick decimal or hex output for encoding, and enter your text. Decoding accepts both &#NN; and &#xNN; forms mixed with plain text.
References like A (decimal) or A (hex) that stand for a character by its Unicode code point, so any character can appear safely in HTML.
To embed characters that would otherwise break markup, or to include symbols and emoji without worrying about file encoding.
Both are equivalent; decimal (😀) is common, hex (😀) matches Unicode's U+ notation. Decoding handles either.