From theregister.co.uk
Google has stopped claiming that an identifier it uses internally to track experimental features and variations in its Chrome browser contains no personally identifiable information.
In February, Arnaud Granal, a software developer who works on a Chromium-based browser called Kiwi, claimed the X-client-data header, which Chrome sends to Google when a Google webpage has been requested, represents a unique identifier that can be used to track people across the web. As such, it could run afoul of Europe’s tough privacy regulations.