What is the ruling on watching pornography on Ramadan nights, and does that affect the fast?

Watching pornography is forbidden, both during and outside of Ramadan. In Ramadan, its prohibition is even stricter, and it contradicts the wisdom of fasting (piety). It does not invalidate the fast, but it affects its reward. The Messenger of Allah (peace be upon him) said: "Whoever does not abandon false speech and acting upon it, Allah has no need of his abandoning his food and drink."

The prevalent characteristic of those who watch it is a lack of piety, and it may lead them to other forbidden acts, such as casting glances at women, or masturbation, which invalidates the fast, or engaging in intercourse with one's wife during the day, which necessitates expiation.

The perpetrator must repent and seek forgiveness, for Allah accepts the repentance of His servant and replaces his bad deeds with good ones. Whoever reaches Ramadan and is not forgiven is indeed lost and has failed.