X-Trace is a network diagnostic tool designed to provide users and network operators with better visibility into increasingly complex Internet applications. It does this by annotating network requests with metadata that can be used to reconstruct requests, even those that make use of multiple network layers. X-Trace “enabled” Internet sites make use of these identifiers to record the path that requests take through their network.
The original X-Trace project is no longer maintained. The work on X-Trace has continued as a research threat at Brown University. It has largely been superseded by the http://pivottracing.io/ project.