Context: Maintaining the privacy of user data is a concern in software development to satisfy customer needs or to comply with privacy laws. Recent studies have shown that software development approaches still neglect non-functional requirements, including privacy. Concern about privacy may increase in the period between when a privacy law is initially announced and when it is passed into law. During this period, companies will be challenged to comply with the new law. Research has shown that many developers do not have sufficient knowledge to develop privacy-preserving software systems.

Objective: We investigate the level of knowledge and understanding that developers possess regarding privacy. We explore the personal, behavioural, and external environmental factors affecting a developer's decision-making regarding privacy requirements.

Methods: We replicated a study by means of in-depth, semi-structured interviews with thirteen practitioners at six companies. Our data analysis is based on the principles of ‘grounded theory codification’.

Results: We identified nine personal factors, five behavioural factors, and seven external environment factors that are relevant to how software developers make decisions regarding.

Conclusion: Our identification of factors that influence the development of privacy-preserving software systems can be seen as a contribution to the specification of effective methods for securing privacy. © 2022 Elsevier Inc.