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PurposeSpatial messaging is a direct extension to text and other multi‐media messaging services that have become highly popular with the current pervasiveness of mobile communication. It offers benefits especially to mobile computing, providing localized and therefore potentially more appropriate delivery of nearly arbitrary content. Location is one of the most interesting attributes that can be added to messages in current applications, including gaming, social networking, or advertising services. However, location is also highly critical in terms of privacy. If a spatial messaging platform could collect the location traces of all its users, detailed profiling would be possible – and, considering commercial value of such profiles, likely. The purpose of this paper is to present Air‐Writing, an approach to spatial messaging that fully preserves user privacy while offering global scalability, different client interface options, and flexibility in terms of application areas.Design/methodology/approachThe authors contribute both an architecture and a specific implementation of an attribute‐based messaging platform with special support for spatial messaging and rich clients for J2ME, Google Android, and Apple iPhone. The centralized client/server approach utilizes groups for anonymous message retrieval and client caching and filtering, as well as randomized queries for obscuring traces.FindingsTwo user studies with 26 users show that the overall concept is easily understandable and that it seems useful to end‐users. An analysis of real‐world and simulated location traces shows that user privacy can be ensured, but with a trade‐off between privacy protection and consumed network resources.Practical implicationsAir‐Writing, both as an architectural concept and as a specific implementation, are immediately applicable to practical, globally scalable, private group messaging systems. A publicly available messaging platform is already online as beta version at http://airwriting.com Originality/value – Air‐Writing addresses three concerns: flexibility concerning arbitrary messaging applications, user privacy, and global scalability of the associated web service. To the best of the authors' knowledge, previous approaches focus on at most two of these issues, while the authors' approach allows all three requirements to be fulfilled.