It is well known that the European Commission is an important access point for lobbying interest groups. The early stages of policy formulation are often the easiest to influence, while it gets more difficult to adjust in later stages. However, not all interest groups are equally successful in lobbying the European Commission. Several studies have already highlighted different assets of interest groups that possibly contribute to an improved chance of lobbying success. However, no study has included all these factors and tested them through a case study approach. This study researches the lobbying success of Digital Europe, the Football Association Premier League Limited, Article 19, the Free Knowledge Advocacy Group, Ecommerce Europe, Bitkom, EDRi, and the Communia Association for the Digital Public Domain. These stakeholders are chosen based on their differences in the possession of relevant knowledge, staff size, member size, position towards the Commission proposal, public support, lobbying strategy, resources and type. This study took these seven factors from existing literature and compares them in one case study. By testing these factors against the EU Commission proposal on preventing the dissemination of terrorist content online, this study includes a proposal on security related issues. This is relevant because while studying lobbying success, this paper also shows the extent to which non-state actors on a European level can influence issues related to national security. This study found that only the position towards the proposal and the stakeholder type significantly increased chances of lobbying success. Citizen groups were generally more successful in lobbying the Commission than business groups and stakeholders that were in favour of the proposal and therefore faced few countervailing parties were more likely to influence the Commission than stakeholders that were against the proposal and faced many countervailing parties. However, despite this study being a solid case study, there are several recommendations for further research. In order to ensure the reliability of the outcome, it would be recommended to build on this research by conducting a study that includes more stakeholders and possible more cases. In addition, it would be interesting to research whether the results differ when the same study is conducted at the parliament stage or the council stage.