Although the state has not passed laws that forbid people from following any religions, atheism is socially unacceptable. People who have dared to voice their opinion for it has received significant backlash by society and even have been imprisoned for it.
1. Islam
Although Indonesia is not an Islamic state, many of the laws enforced by the government reflect their interests. In parts of Indonesia, the Sharia law is practised, such as Aceh, as opposed to criminal law. In many smaller regions of Indonesia, religion is practised more conservatively. The city folk practice Islam more liberally.
Famous Mosques in Indonesia: Istiqlal Mosque (Jakarta), Baiturrahman Grand Mosque (Banda Aceh) and Masjid Agung Dernak (Demak).
2. Hinduism

Hinduism was born out of the teaching of Lord Brahma, who was considered to be the founder of the universe. Eminent Hindi deities worshipped by the Hindus in the world and Indonesia are Ganesha, Lakshmi, Parvati, Rama, Durga, Krishna and Hanuman amongst a few.
Bali however, stands as an exception. Hinduism is still the main religion of Bali, and you will be able to find the most ardent followers here. The variation found here is unique and unlike anything found in the entire world.
Famous Hindu Temples in Indonesia: Prambanan Temple (Yogyakarta), Tanah Lot (Bali), Uluwatu Temple (Bali), Pura Ulun Danu Bratan (Bali), Sri Mariamman Temple (Medan), Candi Jawi (Jawa Timur) and Sewu Temple (Yogyakarta)
3. Christianity

Famous Churches in Indonesia: Our Lady of Vailankanni Catholic Church (Medan), Santo Fransiskus Asisi Church (Berastagi), Regina Caeli Church (Jakarta), The Palasari Church (Bali), The Pohsarang Church in Kediri (East Java)
4. Konghucu (Confucianism)

His philosophies on life were very simple. He believed that religious practices revolving and related to elders and human are essential and need to be more relevant than idol worship.
Confucianism first arrived in the country during the 17th century and was followed by a massive increase in the political drama, especially during the New Order era. As a result, the government banned religion and forbade anyone from pursuing it. Now, Konghucu followers are less than per cent and are a perishing religion in Indonesia.
Famous Confucian Church in Indonesia: Boen Bio (Surabaya)
5. Buddhism

Indonesia is considered one of the biggest Buddhist sanctuaries in the world. However, Buddhism has always coexisted with Hinduism.
During the fall of the Majapahit Empire, Buddhism saw a significant decline in the number of followers. Most of them converted to Islam or immigrated to different parts of the world. Currently, most of the Buddhist population in Indonesia is comprised of Chinese immigrants.
Famous Buddhist Temples in Indonesia: Borobudur Temple (Central Java), Mendut Buddhist Monastery (Mungkid).
How Indonesia Sees Atheism
The constitution of Indonesia does not support atheism or the rejection of religion in any way. This is mentioned in the law as Pancasila. According to many human rights activists, this is a wrong move on the part of the Indonesian government.As a result of this, people here are not true believers of their chosen religion. They might have opted for religion but do not in any way follow it. It has been noticed in many cases that a few atheists recognise themselves as Muslims or Hindus to avoid the wrath of the public and the government.
Many human activists are persuading the government to overlook discrimination based on religion. Religion in Indonesia has come a long way, but there is still more work to be done so that each human can follow their personal beliefs.