What is the session_id cookie?
session_id is an extremely common cookie name, not tied to a single provider: it's used by web servers, programming frameworks (PHP, ASP.NET, Java, Node.js, and others) and e-commerce or CMS platforms to identify a unique visitor for the duration of a visit. It is set automatically by the application's server-side code, without any third-party script involved.
It appears as soon as a visitor loads the site, or upon the first action that requires preserving state — for example adding a product to the cart, logging in, or filling out a multi-step form.
What data it stores
The cookie's value is typically a randomly generated alphanumeric identifier (a session token) that does not directly contain personal data, but links to a record kept on the server. The exact format varies by platform, so it cannot be generalized.
The data tied to the session (cart contents, login state, temporary preferences) is stored on the site's server, not in the cookie itself. The cookie is only sent to the domain that set it, via the HTTP header on each request to that site.
What it is used for
Its main purpose is technical: it keeps a user's navigation continuous across multiple pages of the same site. Without it, a dynamic site would treat every page load as a brand-new visit, losing the shopping cart, login session, or progress in a form.
For a site administrator, session_id underpins essential functions such as login, checkout, multi-step forms, anti-fraud protection (CSRF), and sometimes server load balancing.
Does it require consent?
In the vast majority of cases, the session_id cookie falls under the strictly necessary category, under the exemption set out in Directive 2002/58/EC (ePrivacy), transposed in Romania through Law 506/2004, and Article 6(1)(f) or (b) GDPR — because it is essential for delivering the service explicitly requested by the user (e.g. shopping cart, login).
- Prior consent is not required when it is used solely for the technical operation of the session.
- It must still be disclosed in the cookie policy, with its purpose and duration.
- If the same name is reused for analytics or marketing purposes (possible in custom implementations), that specific use does require consent.
How to block or delete session_id
A visitor can delete or block this cookie from browser settings (Chrome, Firefox, Edge, Safari — per-site cookie management). Blocking it, however, can break core functionality: the cart empties, the login session is lost, and multi-step forms reset.
For site administrators who want centralized control over all cookies — including checking for any mislabeled as necessary — a CMP platform like CookieFix can automatically scan the site and block scripts from categories that genuinely require consent until it is obtained, while keeping the strictly necessary session cookie functional.
Frequently asked questions
It's a generic cookie name used by many sites and frameworks to maintain a visitor's session state, such as a shopping cart or login status.
No, as long as it is used strictly for the site's technical operation, it falls under the strictly necessary cookie exemption in the ePrivacy Directive and GDPR.
It typically expires automatically when the browser is closed (a session cookie), with no fixed expiration date.
You may lose items in your cart, get logged out, or be unable to complete multi-step forms, since the site can no longer track your visit.