The rapid proliferation of online buying applications has significantly transformed consumer purchasing behaviour, particularly among Generation Z (Gen Z), a digitally native cohort with high reliance on mobile technologies. This study examines the behavioural determinants influencing Gen Z consumers’ adoption and usage of online buying applications in Trichy. Drawing on technology adoption and consumer behaviour theories, the research investigates the impact of app usability, social media exposure, influencer marketing, promotional strategies, trust, and convenience on purchase intention, impulse buying behaviour, consumer satisfaction, and continued usage. Primary data were collected from 300 Gen Z consumers using a structured questionnaire, and Structural Equation Modelling (SEM) was employed to test the proposed relationships. The findings indicate that app usability, social influence, and promotional stimuli significantly influence purchase intention and impulse buying behaviour, while trust and convenience are critical drivers of consumer satisfaction and sustained usage. The study extends existing technology adoption models by incorporating social and promotional dimensions specific to Gen Z consumers and provides practical insights for online retailers and digital marketers seeking to effectively engage this emerging consumer segment.