What a character code actually is
Every character a computer displays - a letter, digit, punctuation mark or emoji - is stored internally as a number. The classic ASCII table covers decimal codes 0-127 (English letters, digits and basic punctuation), while modern text uses the much larger Unicode standard, which this tool supports too, so it works correctly on accented letters and emoji, not just plain ASCII.
Converting in either direction
Enter a list of decimal numbers to convert them into the text characters they represent, or enter plain text to see the decimal code behind every character - both directions use the same underlying character-code mapping, just applied in reverse, which makes this useful whether you're decoding a list of codes you found somewhere or generating codes from text you already have.
Why Unicode support matters beyond plain English text
ASCII's original 128 codes only cover basic unaccented English characters - the moment your text includes an accented letter, a currency symbol, or an emoji, a tool limited to classic ASCII either fails or produces the wrong character. Supporting the full Unicode code-point range means this tool handles that wider character set correctly rather than being limited to the decades-old original standard.
Where decimal character codes show up in practice
Low-level programming, certain data-encoding formats, and troubleshooting text-encoding issues (like mystery characters appearing in imported data) are common places where you need to work with the literal numeric code behind a character rather than the character itself.