Double degree of Master of Science in Science Communication & Systems Engineering, Policy Analysis, and Management / SEPAM: Technology Policy and Management / Department: Engineering, Systems and Services + SEC: Applied Physics / Department: Science Communication - In the era of digital communication, the relationship between businesses and customers has changed. Businesses provide online personalized services within their ecosystem based on customer data, but at the same time, customers are reluctant to share personal information. In this article, an online trust building tool is proposed to increase customer’s willingness to share information. A conceptual model is constructed on the relationship between customers sharing information in an online context and businesses providing online personalized services. Customer conditions for information sharing from the conceptual model are validated by a survey under a selection of Transavia airlines’ customers. After conducting a principal component and linear regression analysis, it is found that these customers do not necessarily find monetary or non-monetary benefits the most important conditions for online sharing information. Moreover, gender and age do not have influence. The factor that appears most important for sharing information relates to trust. Customers with a higher general trust and higher institutional trust, are willing to share more personal information with the company. Therefore, literature on trust building is reviewed and four trust building principles are constructed: experience, security, transparency, and trusted sources. For each of the principles, constructs are identified in literature and validated by exploratory customer interviews. The list of constructs is the input for a trust building tool for companies to increase their online trustworthiness. The tool is a basis for a discussion with businesses. These discussions can create insights in how a business can become more trustworthy in the eyes of the customer, and can as a result lead to gaining more customer information.