Purpose of John's Gospel

Stated Clearly by John

John 20:30–31 NKJV

And truly Jesus did many other signs in the presence of His disciples, which are not written in this book; but these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name.

John was an EYEWITNESS

John was writing about what he had himself seen.