From LQWiki

AFAIK is an abbrev. for “As Far As I Know”. There is a variant AFAICT “As Far As I Can Tell”; where AFAIK suggests that the writer knows his knowledge is limited, AFAICT suggests that he feels his knowledge is as complete as anybody else's but that the best available knowledge does not support firm conclusions.

This article is based, in whole or in part, on entry or entries in the Jargon File.