During the Diwali celebration in Coimbatore, Tamil Nadu, this study investigates the main determinants impacting customer behaviour with regard to online buying on flipkart and Amazon. An excellent time to examine purchasing trends is around the Diwali season, which is characterized by a spike in e-commerce activity. The goal of the study is to determine the factors that influence consumer preferences, such as user experience, brand reputation, delivery speed, product diversity, and price breaks. A survey-based strategy was used, focusing on local residents who frequently shop online. Both descriptive and inferential statistical methods were used to analyse the data. The results indicate that the main motivators are flash sales, festive discounts, and alluring cashback offers. Crucial roles are also played by app performance, seller trust, and ease of navigation. Before making a purchase, consumers have a propensity to evaluate offers across platforms. Amazon is preferred for its variety and dependability, whereas Flipkart is preferred for its electronics and low prices. Purchase decisions are also influenced by peer pressure and cultural considerations. Marketers can use the study's insightful findings to customize their approaches during holiday seasons. It also emphasizes how e-commerce is becoming more trusted in Tier-II cities like Coimbatore. Suggestions are made to improve customer pleasure and engagement. This study advances our knowledge of Indian consumers' seasonal internet buying patterns.