Caphtor is a place referred to in the Bible (Jeremiah 47.4, Amos 9.7) and located by traditional Hebrew sources to have been near Pelusium in the eastern Nile Delta. Some think that Jeremiah’s reference to “the coasts of Caphtor” implied that Caphtor was an island. The late Walter Baucum also identified Caphtor with the Egyptian Kaft-ur in the Delta, once occupied by the Philistines [183.309]. A. H. Sayce, a respected 19th century Assyriologist, among others, also placed Caphtor in the Delta.
Keftiu was an Egyptian placename and since the 18th century has been frequently associated with Crete. Half a century ago James E. Jennings of Akron University wrote a paper in which he concluded that “it appears that there is sufficient evidence to support the contention that Caphtor was Crete”(f).
While many commentators today equate Caphtor with Crete, the evidence is far from clear. As Manuel Robbins points out [856.316], the identification of Caphtor with Crete “is based on not one but a string of assumptions. If any of these assumptions are wrong, the conclusion fails, and these assumptions are shaky.”
Baucum offers evidence that the Egyptians also used Keftiu when referring to north of the Orontes River (Syria), Cyprus, Cilicia (S.W. Turkey) as well as Crete. He also attributes the exclusive association of Caphtor with Crete to Champollion’s guessed at identification of the Philistines as the Sea Peoples! A chapter in a book  by Nissim Raphael Ganor that bluntly states that “The Philistines and the ‘Sea Peoples’, not the same entity” is worth reading for anyone studying this particular controversy(i).
Manuel Robbins has concluded [p336] that the most likely location for Keftiu was either Cyprus, Syria or Eastern Anatolia, but that it is essentially a mystery.
Matters become confused when we find that there is also a popular theory that Caphtor and Keftiu referred to the same place. Robbins disputed such an identification. He offers pictorial evidence from tombs on the west bank of the Nile opposite Thebes that might equally suggest Syria as the home of Caphtor [p334], but this is also far from conclusive.
Frankly, I find all the competing opinions(h) extremely confusing and unsatisfactory and believe that a solution to these conflicting ideas is far from a resolution.
Some others have been in favour of identifying Keftiu with Cyprus, among whom, Immanuel Velikovsky argued(g) that if Cyprus was not Caphtor, then it is the only island of any importance in the Eastern Mediterranean not mentioned in the Bible [039.210]. Caphtor/Keftiu: A New Investigation  by John Strange also supports this identification with Cyprus. Walter Baucum claims that “Keftiu was the coastline from Tyre northwards to Anatolia, and included the islands of Crete and Cyprus” [p107].
Yair Davidy in his Introduction to Baucum’s book[183.x] and his own Lost Israelite Identity [1375.208] claims that there was another Keftiu in Northern Europe. Jürgen Spanuth claimed that Caphtor and the Norse ‘holmr Asgard’ mean the same [015.94], namely, “the island of the heaven-pillar”. More recent support for a Northern Europe Caphtor is offered by Eckart Kahlhofer who, like Spanuth, also claims it as the location of Atlantis and adds that it was also the home of the Philistines!
Making matters worse was the introduction of Atlantis into the discussion, bringing with it its own range of conflicting ideas. There is also a number of commentators, including Bruce Wayne(d) and Alex Hawk(e), who take Keftiu to be another name for Minoan Crete and equate it with Atlantis. Robert Ishoy considers Nuragic Sardinia as Keftiu/Atlantis(b).
Although Plato was the first to use the term ‘Atlantis’, there are antecedents to his account of a drowned civilisation. There is an Egyptian legend, which Solon probably heard while travelling in Egypt, and was passed down to Plato years later. It concerns the island nation of Keftiu, home to one of the four pillars that held up the sky. It was said to be a glorious advanced civilization, which was destroyed and sank beneath the ocean. It has been suggested that Plato embellished Solon’s story from “the land of the four pillars that held up the sky” into “the land of the Titan, Atlas, who held up the sky.” The Egyptian legend refers to an island west of Egypt, but not necessarily west of the Mediterranean. It may be relevant to point here that Crete is more northerly of Egypt whereas some of the suggested Atlantis locations such as the Maltese Islands or Sardinia are in fact located westward.
It seems that the debate(a) regarding the identification of Keftiu is set to continue for some time. Muddying the waters further is a serious claim of a Minoan connection with Japan(c) with a particular reference to the Linear A script!