> For the complete documentation index, see [llms.txt](https://docs.jentis.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.jentis.com/key-features/main-domain-cookie/why-does-it-matter-which-level-the-cookie-is-set.md). # Why does it matter which level the cookie is set? Imagine a user starts their journey on `shop.example.com` and later visits `blog.example.com`. If cookies are set at the subdomain level, their session won’t carry over, making capturing their interactions across these different subdomains difficult. This fragmentation disrupts your ability to analyze cross-domain behavior. The same happens on journeys between subdomains and the main domain. If a user starts their journey on `shop.example.com` and then visits `example.com` with cookies set at the subdomain level (`shop.example.com`), capturing their interactions across both of them won’t be possible. By setting cookies at the main domain level (e.g., `.example.com`), data can be shared across all subdomains. This ensures consistent user sessions, unified tracking, and a clearer understanding of how users engage with your entire digital ecosystem. > The **Main Domain Cookie** feature in JENTIS allows you to configure whether first-party identifiers are implemented at the main domain or subdomain level. This flexibility is essential for businesses managing multiple websites within the same main domain. With just one click, all data can be shared across the main domain and all its subdomains, ensuring consistent user sessions, unified tracking, and a clearer understanding of how users engage with your entire digital ecosystem. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.jentis.com/key-features/main-domain-cookie/why-does-it-matter-which-level-the-cookie-is-set.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.