Fasting is very common among Jains and as a part of Jain festivals. Most Jains fast at special times, during festivals, and on holy days. Paryushan is the most prominent festival, lasting eight days in Svetambara Jain tradition and ten days in Digambar Jain tradition during the monsoon. The monsoon is a time of fasting. However, a Jain may fast at any time, especially if he or she feels some error has been committed. Variations in fasts encourage Jains to do whatever they can to maintain whatever self control is possible for the individual.
Santhara or to "fast unto death": To give up food and water entirely. Not to allude that the monk dies from starvation, the cause being that of readiness to pass on, yet the renunciation of food is merely a process which is undergone to prepare for peaceful death under the Santhara fasting. This is undertaken by someone who has finished all his/her duties and wishes to leave this world peacefully. It gives control over when one dies so everything may be completed and a person may leave of his or her own free will.
Great fasts: Some monks fast for months at a time, following Mahavir, who fasted for over 13 years. Many monks claim to fast for periods of over one year, which continues to baffle mainstream western medical science.
Upvas: To give up only food for the whole day.(starting from previous sunset to 2nd day sunrise - approximately 36 hours)
Chauvihar Upvas: Like Upvas, to give up food as well as water.
Digambar Upvas: One may drink water only once a day, before sunset.
Shvetamber Upvas: One may drink boiled and cooled water after Porsi, provided this is done before sunset.
Tivihar Upvas: One may drink boiled water between sunrise and sunset.
Ekasana: To eat one meal a day at one sitting and drink boiled water as desired between sunrise and sunset.
Beasana: To eat two meals a day in two sittings and drink boiled water anytime between sunrise and sunset.
Ayambil: Eating food once in one sitting. The food contains only cereals and pulses not sprouted and it is spice free and boiled or cooked, without Salt, milk, curds, ghee, oil, oil seeds, or green/raw vegetables, fruits and sugar and its products.
Bela/ Chhath: To give up both food and water or only food continuously for two days.
Tela / Aththam : To give up food and water or only food continuously for three days.
Aththai: To give up food and water or only food continuously for eight days.
Navai: To give up food and water or only food continuously for nine days.
Masakshaman: To give up food and water or only food continuously for a whole month.
Navkarsi: Food and water is consumed a minimum forty-eight (48) minutes after sunrise. Devout Jains brush their teeth and rinse their mouths only after sunrise.
Porsi: Taking food and water after 1/4 (25%) of the day passes.
Sadh-porsi: Taking food and water after 3/8 (37.5%) of the day passes.
Purimuddh: Taking food and water after 1/2 (50%) of the day passes.
Avadhdh: Taking food and water after 3/4 (75%) of the day passes.
Chauvihar: No food or water after sunset till at least Navkarsi next day. Many Jains practise this daily. Many Jains leave food or water before forty-eight (48) minutes of sunset.
Tivihar: Like Chauvihar, but one may drink water.
Navapad Oli: During every year for 9 days starting from the 6/7th day in the bright fortnight until the full moon day in Ashwin and Chaitra months, one does Ayambil. This is repeated for the next four and half years. Ayambils may be restricted to one kind of grain per day.
Varsitap: To eat on alternate days and Upvas on the rest, for a whole year. Thus this fast is very rigorous since it entails a whole year of "tap" with eating no food on alternate days and eating food on rest of the days, while following the prescribed rules like not eating in the evening after sunset, not eating root vegetables (like potatoes, onions, ginger), and various other rules. In Swetamber Varsitap they do Ekasanu alternate days and Upavas on the rest days.
Partial fasting (unodar): Eating less than you desire and to simply avoid hunger.
Vruti Sankshep: Limiting the number of items eaten.