Excerpt from Catholic Answer :
“It was not until the Councils of Hippo and Carthage that the Catholic Church defined which books made it into the New Testament and which didn’t. Probably the council fathers studied the (complete) Muratorian Fragment and other documents, including, of course, the books in question themselves, but it was not until these councils that the Church officially settled the issue.
The plain fact of the matter is that the canon of the Bible was not settled in the first years of the Church. It was settled only after repeated (and perhaps heated) discussions, and the final listing was determined by Catholic bishops. This is an inescapable fact, no matter how many people wish to escape from it.”