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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 www.example.com:
Same origin (best practice)
Subdomain
Default domain
Example URL
https://www.example.com/metrics
https://metrics.example.com
https://metrics.run.app
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.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-06-27 UTC."],[[["\u003cp\u003eThis article guides developers on hosting server-side tagging in a first-party context for enhanced security and cookie durability.\u003c/p\u003e\n"],["\u003cp\u003eAchieving same-origin serving involves configuring your tagging server and website to run on the same domain, which can be done using a subdomain or by forwarding requests to a specific path on your main domain.\u003c/p\u003e\n"],["\u003cp\u003eServer-side tagging hosted on the default domain lacks access to crucial server-set cookie benefits, unlike same-origin setups.\u003c/p\u003e\n"],["\u003cp\u003eSetting up same-origin serving requires updating DNS entries or configuring a CDN/load balancer, depending on the chosen method.\u003c/p\u003e\n"],["\u003cp\u003eBefore implementing same-origin serving, ensure you've established a server container in Tag Manager and set up a tagging server.\u003c/p\u003e\n"]]],["To leverage server-set cookie benefits, host your tagging server in the same first-party context as your website. Options include using the same origin (e.g., `www.example.com/metrics`) or a subdomain (e.g., `metrics.example.com`). Both allow full cookie access, unlike the default provider-hosted domain. Implementing same-origin requires a CDN/load balancer and potential DNS updates, while subdomains only need DNS adjustments. Pre-setup of a server container and tagging server is required.\n"],null,["# Custom domain configuration\n\n\u003e This article is for developers who want to host server-side tagging in the\n\u003e same [first-party context](https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#tracking_and_privacy) as their website. Same-origin serving is a best\n\u003e practice that lets you leverage the security and durability benefits of\n\u003e server-set cookies. The below instructions apply for setting up same-origin\n\u003e serving regardless of the Google tag deployed on your site (gtag.js or\n\u003e gtm.js).\n\nWhen you first set up a tagging server, it is hosted on a domain provided by the\ncloud provider. When you use the default endpoint, it delivers data to the\nserver container, but runs in a third-party context. To unlock the benefits of a\nfirst-party context, such as more durable cookies, your tagging server and your\nwebsite have to run on the same domain.\n\nThe table below illustrates how you can host a tagging server when the parent\nwebsite is hosted on `www.example.com`:\n\n| | Same origin (best practice) | Subdomain | Default domain |\n|--------------------------|---------------------------------------------------------------------------------------|--------------------------------------------------|--------------------------------------------|\n| Example URL | `https://www.example.com/metrics` | `https://metrics.example.com` | `https://metrics.run.app` |\n| Server-set cookie access | Full access to security and durability benefits. | Full access to security and durability benefits. | **None.** Can only set Javascript cookies. |\n| Setup complexity | Configure a CDN or load balancer to forward requests. May need to update DNS entries. | Update DNS entries. | Comes pre-configured. |\n\nPick your implementation option to get started.\n\nSubdomain Same origin\n\nPrerequisites\n-------------\n\nThis guide assumes that you have:\n\n- Set up a server container in [Tag Manager](/tag-platform/tag-manager/server-side/overview#create_a_tag_manager_server_container)\n- [Set up a tagging server](/tag-platform/tag-manager/server-side/overview#set_up_a_tagging_server)\n\nConfigure the custom domain\n---------------------------\n\nPick an implementation option."]]