Why "allready" doesn't make the cut

What kind of error is it?

Spelling error

Why do people make this mistake?

The error occurs due to a phonetic misconception. People often write "allready" because the word is pronounced in a way that sounds like the two words "all" and "ready" combined, but the correct form is "already".

What is correct?

The correct spelling is "already", which is an adverb meaning "by this time" or "before now".