HTTP Header "X-NewRelic-ID"... What is it?

Question

I am seeing some requests coming through one of my sites that have the X-NewRelic-ID request header attached. It's always in the form of a header.

Does this identify a user or simply a unique request passing through one of their services?

Thanks

Answer 1

This is the cross application tracing feature header.

https://newrelic.com/docs/traces/cross-application-traces

Answer 2

This header is related to a product called NewRelic.

As mentioned in tutsplus:

NewRelic is a managed service (SaaS) that you “plug in” to your web app, which collects and aggregates performance metrics of your live web application.

This header is automatically added by that plugin and also it has some scripts injected on all pages (if requested by owner) to monitor web page usages in client browser and gather data and send them back to the server for monitoring and statistical analysis..