In this proposal, two studies on users’ motivations for contribution in online platforms are presented. The first study aims to investigate users’ dynamic contribution pattern in reward- based crowdfunding. We construct our unique dataset based on bi-hour crawling of project- related information from Kickstarter. By analyzing backers’ contribution and referral patterns before, during, and after the threshold, we show that users are more likely to help rather than to pre-order the projects. The second study focuses on the effect of monetary incentive on users’ voluntary contributions in Q&A platform. We find monetary intervention can create a positive spillover effect on users’ free content creation. Our results provide support that users contribute in order to improve their reputation. Overall, these two studies contribute to a better understanding of users’ motivations for contribution in crowdfunding and Q&A platforms. They have direct managerial implications to platform owners.