Is it true that there is no evidence that the Quran had a written form in the seventh century?

This statement is false, uttered by those who assail Islam to turn people away from it. It suffices that Allah Himself guaranteed the preservation of the Qur’an, saying: (Indeed, it is We who sent down the Dhikr (the Qur’an), and indeed, We will be its guardian.) [Al-Hijr: 9]. Furthermore, the continuous transmission of the Qur’an, both orally and in writing, is well-known to anyone with even the slightest knowledge of Islamic sciences. People continue to receive it through oral transmission with chains of narration (asanid) back to the Prophet, peace be upon him. Among the wonders of Allah’s preservation of the Qur’an is that anyone who attempts to distort it is inevitably exposed.

Everything that was revealed to the Prophet, peace be upon him, was written down immediately, and some Companions had their own copies of the Qur'an. After the Prophet's death, Abu Bakr al-Siddiq compiled the Qur’an into sheets, and then Uthman ibn Affan gathered it into Mushafs (codices) based on those sheets and on memorization. Uthman sent copies of the Mushaf to the main Islamic centers to serve as a reference for them. Additionally, there are numerous ancient manuscripts of the Qur'an that attest to the existence of preserved copies proving that no alteration has occurred to it. Allah Almighty says: (Falsehood cannot approach it from before it or from behind it; [it is] a revelation from a [Lord who is] Wise and Praiseworthy.) [Fussilat: 42].