Personalization in e-commerce has so far been server-centric, requiring users to create a separate individual profile on each server that they like to access. As product information is increasingly coming from multiple and heterogeneous sources, the number of profiles becomes unmanageably large. We present SmartClient, a technology based on constraint programming where a thin but intelligent client provides personalized information access for its user. As the process can run on the user's side, it allows much stronger filtering and visualization support with a wider range of personalization options than existing tools. It also eliminates the need to personalize many sites individually with different parameters, and supports product configuration and integration of different information sources in the same framework. We illustrate the technology using an application in travel e-commerce, which is currently under commercial deployment.