The evidence of Irenaeus and Polycrates points to the city of Ephesus. Others have suggested that it originated in the city of Alexandria in Egypt. Some scholars who see a link between the Gospels of Matthew and John have favoured Antioch.
Nevertheless the weight of opinion is still in favour of Ephesus.

In 1920 a piece of papyrus manuscript was found. It is usually referred to as the Rylands Fragment of the fourth gospel. Its discovery proves that John's gospel was circulating in Egypt around 130AD.
If we allow a generation for the book to travel from Ephesus and become known in Egypt, then it could not have been written later than 100AD. How early the gospel may be dated depends on whether or not one thinks that the author knew the gospels of Mark and Luke.

If the author knew them (Streeter's claim) then the date of composition of the fourth gospel can hardly have been earlier than AD90.
If he did not know them then the gospel could be much earlier.

How much earlier than AD90 depends on a solution being found to the question of authorship.

John Robinson has suggested that the gospel contains a good deal of reliable historical information. He wishes to ascribe to the work a very early date.

Irenaeus, Bishop of Lyons claimed "John the disciple of the Lord, who leaned on his breast, himself issued the gospel while living at Ephesus."
This testimony is supported by the Muratorian Canon, Polycrates of Ephesus, Clement of Alexandria, Tertullian and Origen.
What makes Irenaeus' testimony so strong is the fact that as a boy he heard Polycarp tell of his friendship with John the disciple of the Lord. .

There is a rather late piece of evidence that John the disciple was martyred soon after his brother James.

The witness of the early Church Father Papias is somewhat confusing. Papias 135AD refers to two Johns "I was accustomed to inquire about the sayings of the presbyters, what Andrew or what Peter had said or Philip or Thomas or James or John or Matthew or any other of the Lord's disciples; and what Ariston and the presbyter John, the disciples of the Lord say." Two people seem to be involved in this statement, both named John. One was part of the twelve and was no longer living. The other is known as the Elder/Presbyter and is still alive. This possibility is fuelled by the fact that the author of the epistles is called "the Elder"

Internal evidence

In 19:34f the author adds "This is vouched for by the evidence of eye-witnesses, whose evidence is to be trusted." Although the eyewitness is not named, the fact that a few verses later the "beloved disciple" is mentioned as present at the foot of the cross seems to be significant.

In 21:24 "It is the same disciple who attests what here has been written. It is in fact he who wrote it, and we know that his testimony is true.

There have been several answers to this question.
Lazarus, John Mark, the rich young ruler etc.
By far the most likely candidate would seem to be John the son of Zebedee.

1. Except in John 21:2 the son of Zebedee is not mentioned in the gospel. Yet this man, according to all the synpotics was one of the inner circle of Jesus' disciples.

2. The close association between Peter and the Beloved Disciple 13:23f, 20:2f, fits the character John so well.

20:31 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."

Other scholars have suggested that the gospel seems to present a picture of a Jesus who was not looking for a future coming in power. Eschatology does not play a large part in the gospel message and themes such as kingdom of God, so prevalent in the synoptic works is missing from the fourth gospel.