What survives a hop

One hop

A first-party cookie stays on the host that set it. A UTM stays only if the next URL still has the query. A referrer policy decides how much of the previous URL is visible. _gl is a linker parameter a tag can add so the next host can read a client id. This page builds a toy linker. It is not Google’s.

What arrives

URL

https://shop.example/welcome?utm_source=lab&utm_medium=demo&utm_campaign=cross-domain&_gl=1*demo*cid*123.456

Cookie

bbp.visitor on www.blackboxpersonalization.com is not sent. The other host has no copy.

UTM

utm_source=lab is still on the URL.

Referrer

https://www.blackboxpersonalization.com/

Linker

_gl is on the URL. The next page can read it if its tag looks for it.