Among Śvetāmbara Jains there are two very different groups:

1. Ascetics (sadhus–sadhvīs / monks–nuns)

- Śvetāmbara monks and nuns wear simple white cloth prescribed in their code of conduct. - The clothes are minimal, loose and modest – meant only for covering the body and reducing attachment. - Details like “underwear” in the modern sense are not the point of the scriptures, so traditional texts speak only of the required outer garments, not about modern innerwear. - Different gacchas/sects may have slightly different maryādā (rules), but all focus on simplicity, modesty and non‑attachment, not fashion or comfort.

1. Laypeople (śrāvaks–śrāvikās)

- Śvetāmbara householders wear normal, modest clothes according to local culture: kurta–pyjama, sari, salwar‑kameez, shirt–trousers, etc. - Wearing or not wearing modern “underwear” is just a social and health choice, not a religious rule. The Jain focus for laypeople is that clothes should be: - clean - simple and not showy - modest (properly covering the body) - as non‑violent as possible (avoid leather, silk, etc.) ( jainknowledge.com)

So:

• For monks/nuns: the question is not usually framed as “underwear vs no underwear”, but “strict, simple white ascetic dress as per maryādā.”
• For ordinary Śvetāmbara Jains: yes, they generally follow normal modern clothing customs; Jain dharma mainly adds guidelines of modesty, simplicity and non‑attachment, not detailed rules on inner garments.