A system can effectively compress instrumentation data related to a page view on a client-side application thread (such as a web browser thread) and communicate the compressed data over the Internet to a server (such as an analytics server). Leading up to the compression, the system can include data scanning, code building, code encoding, and code serialization. The compression can run on a background thread of the client-side application, so that it does not interfere with other processes run by the client-side application. For example, a web worker can implement the code compression described herein.