# 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.


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