Is it forbidden to fast on all three days of Eid al-Fitr, or just the first day?

It is forbidden to fast on the day of Eid al-Fitr only in Shawwal. It is recommended to fast six days of Shawwal, starting from the second day of the month. It is forbidden to fast on the day of Eid al-Adha and the three days of Tashreeq that follow it, except for those who cannot find a sacrificial animal, according to some jurists, while others absolutely forbid fasting on these days. Eid al-Fitr is only one day.