Matt Damon was 29 in Jay and Silent Bob Strike Back when he played the character 'Matt Damon / Will Hunting (uncredited)'.
That was over 23 years ago in 2001.
Today he is 53, and has starred in 110 movies in total, 83 of those since Jay and Silent Bob Strike Back was released.
In Jay and Silent Bob Strike Back, I think Matt Damon looks: