1QIsa is generally in agreement with the Masoretic codices such as the Alleppo Codex. (1)
Between 'The Great Isaiah Scroll' 1QIsa and Masoretic codices the number of textual variants is well over 2,600, however, according to scholar scrutiny these variants are minor and 1QIsa is 95% identical to Masoretic text. Variants ranging from a single letter, sometimes one or more words, to complete variant verse or verses. For example, the second half of Verse 9 and all of Verse 10 in the present Masoretic version of Chapter 2 are absent from the Great Isaiah Scroll in the Israel Museum's full manuscript that you see here online. The same verses, however, have been included in other versions of the Book of Isaiah in the scrolls found near the Dead Sea (4QIsaa, 4QIsab), and the Hebrew text from which the ancient Greek version or Septuagint (3rd-1st century BCE) was translated. This confirms that these verses, although early enough, were a late addition to the ancient and more original version reflected in the Great Isaiah Scroll. (1)
Though variants between 1QIsa and Masoretic codices include alternative spellings, scribal errors, and corrections, no alterations to the texts meanings, nor to messianic beliefs are demonstrated.
“Even though the two copies of Isaiah discovered in Qumran Cave 1 near the Dead Sea in 1947 were a thousand years earlier than the oldest dated manuscript previously known (A.D. 980), they proved to be word for word identical with our standard Hebrew Bible in more than 95 percent of the text. The five percent of variation consisted chiefly of obvious slips of the pen and variations in spelling.” -Gleason Archer (2)
“It is a matter of wonder that through something like one thousand years the text underwent so little alteration. As I said in my first article on the scroll, ‘Herein lies it's chief importance, supporting the fidelity of the Masoretic tradition.'” -Millar Buruows (3)
"A comparison of the Qumran manuscript of Isaiah with the Massoretic text revealed them to be extremely close in accuracy to each other: "A comparison of Isaiah 53 shows that only 17 letters differ from the Massoretic text. Ten of these are mere differences in spelling (like our "honor" and the English "honour") and produce no change in the meaning at all. Four more are very minor differences, such as the presence of a conjunction (and) which are stylistic rather than substantive. The other three letters are the Hebrew word for "light." This word was added to the text by someone after "they shall see" in verse 11. Out of 166 words in this chapter, only this one word is really in question, and it does not at all change the meaning of the passage. We are told by biblical scholars that this is typical of the whole manuscript of Isaiah." -R. Laird Harris (4)
(1) The Israel Museum, Jerusalem
(2) Archer, Gleason. A Survey of Old Testament Introduction. Chicago: Moody Press, 1985.
(3) Millar Burrows, The Dead Sea Scrolls (New York: Viking Press, 1955), 304, quoted in Norman Geisler and William Nix, General Introduction to the Bible (Chicago: Moody Press, 1986), 367.
(4) R. Laird Harris, Can I Trust My Bible? (Chicago: Moody Press, 1963), 124.