All four Gospels were published anonymously because the authors were known to the communities. After all at that time - in the first century AD - Christian communities were small.
The titles - “according to Matthew, Mark, Luke, John” - were attached in the 2nd century when the four Gospels were gathered together and began to circulate as one collection.
The Gospel alone does not mention its author - the same goes for the other Gospels.
Interestingly enough, the Gospel alone does not mention the name of John the apostle, although it mentions the names of some other apostles (see John 1:40–49; 11:16).
Instead, the gospel mentions “the beloved disciple” that appears in the accounts related to last part of Jesus’ earthly life (John 13:23; 19:26; 20:2; 21:7,20).
From the time of early church, this “beloved disciple” was identified as John the apostle, the son of Zebedee, one of the twelve. We have the testimonies from St. Irenaeus of Lyon and St. Clement of Alexandria.
However, from the middle of eighteen century his authorship was being questioned and the scholars put some candidates for the author of the Gospel - the apostle Thomas, Mary Magdalene, Lazarus, “John the Elder/presbyter”.
There are no proofs, however, that any of them was ever considered as its author. Finally, there are those who indicate that he represents those who believe in Christ - which is again doubtful.
“The beloved disciple”
According to the synoptics there were only twelve disciples present at that event (Mk 14:17).
He cannot be identified with Peter (see 13:24, 20:2), neither with other disciples mentioned by name.
In the epilogue (John 21:1–3), he is among the seven disciples.
In that event, he is distinguished from Peter (John 21:7,20) and from Thomas and Nathanael. He can be either one of the sons of Zebedee (whose names are not given) or one of the other disciples listed but not named.
He cannot be James, because James was put to death by Herod Agrippa I during his reign between 41–44 AD (Acts 12:1f). In that case, he would not be able to write the Gospel.
In the early days of the Church John appears repeatedly as a companion of Peter (Acts 3:1–4:23; 8:15–25; cf. also Gal 2:9 - Peter, John, and James - the Lord’s brother - as the pillars of the Jerusalem community).
Together with Peter and his brother James, John belonged to the inner circle of the disciples of Jesus (Mk 5:37; 9:2; 14:33).
John 18:15–16 - mentions “another disciple” who was known to the high priest who brings Peter into the courtyard.
John 19:35 in connection with John 19:25–27, that he was the eyewitness of Jesus’ crucifixion.
The Gospel of John preserves authentic but an independent historical tradition.
The Gospel probably began to form in Palestine but its present formed achieved in a non-Jewish context.
There is an ancient tradition that the Apostle John spent his last years in Ephesus.
Finally, the redaction of the Gospel has to be placed between 65/66 AD - the death of Peter and 135 AD - the date of a NT manuscript p52.
Some indicate that the final relation of the Gospel had to come after year 90 AD when the link between Judaism and Christianity disintegrated.
The earliest known fragment of any part of NT is a tiny piece of one leaf of what was once a codex of the Gospel of John. It contains a few words from John 18 and is dated about 130 AD. It is listed as Papyrus 52.
In the earlier part of the 2nd century the Fourth Gospel was already been quoted by the Fathers of the Church.
St. Justin Martyr (100 - 165 AD) quotes John 3:3–5 - probably from memory - in his teaching about baptism. He also taught a lot about “Logos” - the pre-existent Word of God that became incarnate in Jesus Christ.
Tatian, a disciple of Justin, wrote Diatessaron a work that tried to harmonise all the four Gospels. In that work, the Gospel of John provided the framework into which material from other Gospels was fitted at appropriate points.
Towards the end of the second century in the Muratorian Canon - the earliest known catholic list of NT books - we find such an account of the origin of the Fourth Gospel:
“John, one of the disciples, wrote the Fourth Gospel. When his fellow-disciples and the bishops urged him to do so, he said, ‘Join me in fasting for three days, and then let us relate to one another what shall be revealed to each’. The same night it was revealed to Andrew, one of the apostles, that John should write down everything in his own name, and that they should all revise it”.
Then further in that fragment, the author quotes 1 John 1:1, 3a pointing out the the fourth Gospel was written by an eyewitness of the Lord’s wonders.
Finally, we have the testimony of St. Irenaeus (born 130 AD) who after 177 AD became bishop of Lyon and so moved from Asia to Europe.
He compares the four Gospels to the four quarters of the world - today we would say to the four cardinal points of the compass.
In his writing, we find the statement: “John the disciple of the Lord, who leaned back on his breast, published the Gospel while he was resident at Ephesus in Asia”. There is reference to John 13:23 here.
St. Irenaeus relies on the testimony of St. Polycarp who was at least 86 years old at the time of his martyrdom in AD 156. Irenaeus wrote that he still remembers how Polycarp said about his personal conversations with John and with the others who had seen the Lord.
Finally, we have the testimony of St. Clement of Alexandria - a contemporary of St. Irenaeus - who says that after the first three Gospels had been written, ‘John, last of all, conscious that the bodily (i.e. external) facts had been set forth in those Gospels, was urged on by his disciples and, divinely moved by the Spirit, composed a spiritual Gospel’.
The usual one:
There are others division that are more detailed.
The main characteristics of the fourth gospels are the signs, the long dialogues and monologues and the so-called priestly prayer of Jesus.
The seven signs are:
Number seven is significant.
See also the “seven days” (John 1:29, 35,43; 6:22; 12:12).
Finally - The High Priest Prayer in John 17.
And there are many similarities in the story of Jesus’ passion and resurrection.
But overall, the Gospel of John defers from the synoptic Gospels in style and the way he presents Jesus Christ.
The theologians speak about “low christology” of the synoptic Gospels and “high christology” of John’s Gospel.
The purpose of the Gospel is stated in John 20:23 - bringing the readers to faith.
Faith involves both believing in Jesus and believing that He is the Christ, the Son of God.
Thus, eternity entered this world. The life of the eternal Word of God was the life of a real human being of flesh and blood. Moreover, the events in which Jesus revealed the Father were also historical events - in particular the events that took place on April day about 30 AD - his passion - that express the outpouring of divine love.
John presents Jesus as being sent by the Father - He is the full revelation of the Father. Jesus wants to draw all to the divine relationship that exists between Him and the Father (John 14:23).
John 3:16 - Behind the message of the Gospel is the love of God from humanity. Jesus is the eternal Word, eternal Son of the Father, incarnated in a human life and sent into the world for the world’s salvation. It is accomplished in Jesus’ laying down his life on the cross.
Jesus is presented most of all as the Son of God (John 1:34, 49; 10:36, 20:31). It was the proclamation of this truth that led to Jesus’ death (John 19:7).
Jesus’ death on the cross is also his exaltation (lifting up) (John 3:14; 12:32,34).
For those who believe in him and in the one who sent him, Jesus brought eternal life (John 3:15, 36; 5:24; 6:40).
Water (John 4:14) and the food (John 6:27) coming from Jesus give eternal life, but he himself is the source of life (John 11:25).
Jesus is also the light (John 8:12; 12:46) that dispels the darkness of evil and sin.
Action and Words
It is important to note that both Jesus’ actions and words are the vehicle of revelation.
The Evangelist records words which were really spoken, actions which were really performed. His records of these words and actions includes their interpretation. The interpretation discloses their inner meaning and moves us to believe that Jesus is the Revealer of the Father and the Saviour of the world.
The Holy Spirit (see John 14:26; 16:13).
It is also the Holy Spirit who illumines the readers to recognise in that Gospel the authentic voice of Jesus, to transform the readers into spirit and life filled Christians who in today’s world will communicate the saving message of the Gospel.
Lastly, in the last century some scholars spoke about “the community of the beloved disciple”? But, the question is: was there such community? We simply do not have enough data to know.