|In this era, distance and time is not a barrier anymore to get an information. News, commercials, sales, purchasing, and other information can be obtained through the internet. Internet penetration in Asia, especially in Indonesia, has been increasing along with the passing of time. Assess the great potential of internet use in Indonesia, many retailers are now starting to commit an innovation in marketing of their products and services, by expanding to the online world. The purpose of this research is to analyze the usability dimensions in some of the B2C and C2C e-commerce sites that were being tested, according to the tasks that were given. This study also aims to identify which UX variable is significantly affect the UX satisfaction value on each site. Experimental methods and UX questionnaire distribution are being used in this research. The result of this research is “Task 3” is easier and faster to be operated on B2C site while the other four tasks are easier and faster to be operated on C2C site. Moreover, pertaining to a forming of multiple linear regression models, variables that significantly and positively affect the UX satisfaction value for B2C sites are “Classic Aesthetics” and “Service Quality”, and only “Service Quality” for C2C sites.