Within the Puranic tradition, the distinction between Mahapuranas and Upapuranas is primarily one of status, scope, and function. The Mahapuranas are regarded as the major or principal Puranas, traditionally fixed at eighteen in number and treated as primary canonical texts. They are more widely recognized as authoritative and are frequently cited in theological, philosophical, and ritual contexts across different schools of Hindu thought. Upapuranas, also traditionally counted as eighteen, are considered subsidiary or secondary texts whose lists and recognition vary more from source to source, and whose authority is generally regarded as lower or more localized.

The Mahapuranas characteristically adopt a broad, almost encyclopedic range of themes. They address the creation and dissolution of the universe, the cycles of time, and the genealogies of gods, sages, and kings, while also narrating the deeds of major deities and their incarnations. Alongside cosmology and myth, they expound dharma, pilgrimage traditions, and sacred geography, thereby offering a kind of panoramic vision of the religious universe. Many of them are understood to follow the traditional set of defining characteristics, such as accounts of creation, re-creation, lineages, cosmic cycles, and royal dynasties, which together give them a comprehensive and structured character.

By contrast, the Upapuranas tend to have a more specialized and focused orientation. They often center on particular deities, sectarian traditions, or ritual systems, such as those devoted to specific forms of the divine or to particular vows and observances. Some are closely tied to regional traditions, local sacred sites, or specific communities, elaborating themes that the Mahapuranas may only touch upon briefly. Their organization is generally more flexible, and they do not typically claim the same exhaustive scope as the major Puranas, even when they are extensive and influential within their own circles.

From a spiritual and interpretive standpoint, the Mahapuranas can be seen as offering a shared, pan-Indian narrative framework, within which the grand patterns of cosmology, myth, and dharma are articulated for a wide audience. The Upapuranas, in turn, function as more focused lenses, bringing particular forms of devotion, regional sacred landscapes, and specialized practices into sharper relief. Together, they form a layered scriptural landscape: the Mahapuranas providing a broad horizon of meaning, and the Upapuranas deepening and diversifying that horizon through more specific, often sectarian or regional, elaborations.