Custom domain configuration

This article is for developers who want to host server-side tagging in the same first-party context as their website. Same-origin serving is a best practice that lets you leverage the security and durability benefits of server-set cookies. The below instructions apply for setting up same-origin serving regardless of the Google tag deployed on your site (gtag.js or gtm.js).

When you first set up a tagging server, it is hosted on a domain provided by the cloud provider. When you use the default endpoint, it delivers data to the server container, but runs in a third-party context. To unlock the benefits of a first-party context, such as more durable cookies, your tagging server and your website have to run on the same domain.

The table below illustrates how you can host a tagging server when the parent website is hosted on

Same origin (best practice) Subdomain Default domain
Example URL
Server-set cookie access Full access to security and durability benefits. Full access to security and durability benefits. None. Can only set Javascript cookies.
Setup complexity Configure a CDN or load balancer to forward requests. May need to update DNS entries. Update DNS entries. Comes pre-configured.

Pick your implementation option to get started.


This guide assumes that you have:

Configure the custom domain

Pick an implementation option.